There are so many places Sumner could begin his tale. He could begin on July 29 1980, in a Manchester club called the Beach where he and his two fellow surviving members of Joy Division, Morris and bassist Peter Hook, are about to make their stage debut as New Order. It is 10 weeks since Joy Division's singer Ian Curtis hanged himself in his Macclesfield home, 10 weeks since the 23-year-old Curtis turned the lights out on a life blighted by epilepsy, its medication and a faltering marriage. Tonight is not only the first time that guitarist Sumner will perform without his friend, it's the first time he'll sing publicly. "I'm shitting myself," he says, understandably.

"That is a defining moment," suggests Hook, helpfully.

But no. Sumner can think of happier places to start. Such as in a recording studio in London in 1982, where Sumner, his mind bent slightly out of shape by the effects of a mild dose of LSD, is about to put the finishing vocal touches to Temptation, the first New Order single to step out of Joy Division's imposing art-rock shadow and head optimistically towards the dancefloor instead. Just as he's about to start singing, Hook rushes in from the snow storm outside and stuffs a snowball down his singer's shirt. Listen carefully and you can pick out Sumner's startled yelp during the song's intro.

That doesn't seem to Sumner an appropriate place to kick off either, though. He's been working with Hook (alright, everyone except his immediate family calls him Hooky, and so shall we) and Morris for 25 years, he's got a New Order box-set to promote and he wants to hit the right note. He wants to sum up the band. Maybe he should head to New York, 1983, where the electro pulses from the city's nightclubs are helping New Order invent Blue Monday, the largest-selling 12-inch single of all time (although it's packaged in a sleeve so expensive that every time the band sell a copy, they lose money).

Or to Ibiza, in 1989, where New Order have decamped to record their fifth studio album, Technique, on the advice of Hooky, who has scouted out the location with this recommendation: "The studio's shit, but it's got a pool and a bar." New Order did a lot of sunbathing during those sessions, visited all the local nightclubs, enjoyed the studio's hospitality ("the barman used to stick two tabs of acid in his eyeballs and carry on serving"), wrote off their hire car, and recorded little more than a few drum tracks. The experience gave the band a new lease of life, but it's no place to kick off this story.

Maybe, considers Sumner, they should begin where it all so nearly ended, stuck in a traffic jam before a stadium show outside New York in 1993. The band have just agreed that they can't stand the sight of each other. They're going to quit. The reasons for the split are myriad and complex. Their label, Factory Records, has recently been sunk by the financial holes drilled in its hull by its two loss-making side projects, the legendary Hacienda nightclub and Dry 201 bar in Manchester, taking all of New Order's hard-earned investment with it. But business fears are not the band's sole anxiety. Heavy cocaine use and antipathy had blighted the recording of the forthcoming Republic album and was now informing the mood of the tour too.

At a meeting that afternoon they'd agreed to knock it on the head, with Sumner's parting shot to Hooky being: "If I never see your face again, it'll be too soon." Yet he would have to see him again on the remaining few dates of the tour. In separate limos, in a traffic jam generated by their fans, the pair both start to sob.

"I was relieved," says Sumner.

"I was devastated," says Hooky, however. "It was a bloody tragedy. We'd never sounded better."

If the story doesn't start at that dead end, it's got to begin at the new dawn, with New Order's reunification and last year's rollicking comeback album, Get Ready. After years without any contact between the factions in the group, the band's manager, Rob Gretton, finally managed to entice them together in 1998 to consider some festival offers. After five minutes, all present agreed there weren't really any problems and they should, you know, maybe start seeing each other again. In 2000, recording on a new album began and, despite the twin blows of Gretton's death from a heart attack and Gilbert's resignation to look after her seriously ill daughter, the band discovered new harmony in the studio.

"That was probably the happiest I've ever been with these fuckers," chortles Hooky. "At the time I could've murdered him for saying it, but Sumner was right all along. We needed time to find ourselves. Now, if something's on our minds, we just say so. Miles better."

Sumner has a different idea about where he wants his story to start. He wants to begin with a cautionary tale for anyone reading this, although he has one reader in particular in mind. He'd like to offer Jamie Oliver some advice. "The story of New Order is all about learning from our mistakes," he begins evenly. "I've been watching that series about Jamie Oliver setting up his restaurant and he's doing exactly what we did with the Hacienda. The similarities are amazing.

"This is how it happens. You invest a hundred grand to start a club. You employ loafers to work there because you want to give them a chance. But they're useless. You get an estimate for the building: triple it. By the end of the first year they go, 'So far it's cost you 175 grand - if you want to see any of that money again we need another hundred grand off you. If you do that, the club will go into profit.' Well, we don't want to lose the 175 grand so we'll go on tour, here's another hundred. It's going into profit now. Then the manager of the club says, 'I've turned it around but I'm not prepared to stay unless you let me open another club.' So we bought the Dry Bar to keep our manager and to tuck us into success. Woof, it goes way over budget. Exactly the same thing all over again."

"How does this have anything to do with the box-set?" asks Hooky. Sumner ignores him.

"We were already bailing out Factory by having any profits we made ploughed straight back in to save the label - not that they told us. And also we were financially keeping the club afloat. I'll give Jamie Oliver one more tip: if you pay anybody cash in hand, don't write it down in a book like they did at Factory. And if you do, don't leave the book at reception when the taxman comes. And when the taxman says 'Have you got the book?' don't give him that book - because it's you, not the bankrupt label, that'll get a hefty fine at the end of it.

"Not that we're bitter. 'Cos we're not. But we are wise after the fact. Take note Jamie."

Hooky spins round on his chair, exasperated. "How does this have anything to do with the box-set?" he demands.

Sumner shrugs. "What can you say about a fucking box-set? Let's be honest. Do you want to read an interview about a box-set? You want to read about New Order. The highs and the lows."

New Order are about to release a four-CD box-set called Retro. Unlike most box-sets, Retro is neither a complete archive of the group's work nor rammed full of rarities. In fact, New Order had little to do with its compilation. They handed that task over to four curators whose opinions they trusted: journalists Miranda Sawyer and John McCready picked The Hits and The Early Years respectively, Mike Pickering of M People chose Remixes, and Bobby Gillespie of Primal Scream chose Live.

It is a magnificent collection, The Hits and Early Years potent reminders of what a pioneering pop group New Order have been - no other band in the modern era has so consistently mapped fresh ways of delivering life-affirming tunes.

Hooky, however, thinks they should just release four blank CDs in shrink-wrapped box-sets. He doesn't think anybody opens them because they're worth more unopened and it would've saved the band money. Morris agrees. "I buy a box-set every Christmas. I never play them. They just sit there looking nice. That's all I want from them."

Hooky: "It's a nice bookend to a career. But it's like when you get model cars and they're in the original box. If you take them out they're devalued. So you have to leave them in the box. I know because I collect them as well. You have your little displays..."

Sumner's eyes light up. "What do you collect?"

"Cars," says Hooky. "Model cars."

Sumner arches an eyebrow. "Oh."

"Well, I like collecting," continues Hooky, furiously scratching his stubble. "I collect everything."

"Then we're different," notes Sumner. "I like to get a skip and throw everything away. A clean slate, that's what I like."

In the future, when looking to remake The Last of the Summer Wine, the BBC should consider New Order as ripping new cast members. Hooky is the roguish, good-natured hound, full of enthusiastic energy and babble. Sumner is the parched dry, moody raconteur, always ready with a rolled-up quip to thwack across Hooky's snout when he gets out of hand. And Morris's weary Stan Laurel shrug masks a sly wit and keen eccentricity. It's his tank and armoured personnel carrier that are parked a little further up the hill after all. Not for him the simpler pleasure of the model car collection.

And they imagine that there are still plenty of adventures for them to undertake together, as a group, up here in the Pennines. For the first time, there's no end in sight.

"I have a hard time getting my head around the idea of playing The Perfect Kiss in my 50s," says Hooky. "I can't quite get there. But you can only do what feels right. I still think we're the greatest band. How can you turn your back on that?"

Tellingly, when asked when and where they were happiest in New Order, they unanimously declare: "Now."

"The best thing about splitting up last time is knowing we won't split up for the same reason again," says Sumner. "It'll end naturally. We've had it large and that was very nice, and then it wasn't. Now we just want to write new songs. What could be better?"