I saw him! I saw him!” yelps a 14-year-old boy to his friend, standing in the drizzling rain by the door to the Bournemouth International Centre, where, inside, Scouting For Girls are conducting a sound check. “I couldn’t see nothing,” scowls his mate. “You were in the bloody way.”

It’s only 4pm, and already queues are forming in the freezing wind outside the venue for tonight’s show. Following extravaganzas from Oasis, Girls Aloud and Jay-Z, Scouting For Girls are kicking off their national tour here, in a week in which they have been crowned bestselling UK band of 2008. Teenage girls in fluorescent legwarmers have turned up, along with mums and dads in sensible fleeces and lads with artfully dishevelled hair.

Two days earlier, the three members of Scouting For Girls are huddled around a fire in a West London pub, looking impressively nondescript. “We’re just painfully normal people,” says the singer Roy Stride. “There’s a guy down my road who reckons I look like the guy who sings in Scouting For Girls.” He laughs. “And now I can’t go into the shop any more, ’cos every time I go in, he starts singing She’s So Lovely, thinking I’m the guy who looks like the guy who sings She’s So Lovely. . .”

To the 100,000 or so fans who have bought tickets for the Scouting For Girls tour, the group’s normality and cheery familiarity is part of their charm. Their piano pop songs (It’s Not About You, Elvis Ain’t Dead) feature choruses so catchy that not singing along is as easy as eating a doughnut and not licking your lips.

In the world of music criticism, however, Scouting For Girls have pretty unanimously been given the thumbs-down. Critics sniffed at the album, and even the teen-geared NME dismissed it as “the sort of music that makes you want to dance and sing along. If you’re an idiot.”

That’s got to hurt, hasn’t it? “To be honest, it doesn’t really bother me,” Stride says with a shrug. “At the end of the day, we’re the bestselling band in the UK this year. We’ve travelled the world, played all over the place. The only thing that I take offence to is people calling our fans idiots. I’m more than happy for them to call me an idiot,” he says. “They may not be far from the truth.”

And of course, one man’s idea of inanity is another’s idea of simplicity and directness – the cornerstones of pop music. As a child, Stride fell in love with pop while sitting in the back of his parents’ car, listening to 1960s hit compilations. He believes that there is a formula to great pop songwriting: “An amazing melody, lyrics which have real feelings in them – and you have to build it up and muck about with it.” It’s a mightily effective formula too. There’s no logical reason why repeating the line “She’s so lovely” seven times should make for an emotionally potent chorus – but anyone who has been to a (non-posh) wedding this year can testify that it’s the sort of song that gets people skidding to the dancefloor.

“I like the songs people play at weddings,” Stride says. “I’ve never been a music snob, someone who knows the B-sides of every damn song. I’ve always loved the big hits.” The bespectacled Greg Churchouse agrees. “We’re a pop band,” he says, “just without the looks.”

Another assumption made of Scouting For Girls (besides the one that they are morons) is that their success is the result of a cunning marketing plan (“Again,” Churchouse says, “look at the faces”). The truth is that the band has been together for over a decade. Stride met the drummer Pete Ellard when Ellard was 6; and he and Churchouse made friends on the first day of secondary school. When the school acquired a drum kit, the pair would stay so late after school that they would have to get out through the windows.

The intention from Day 1 was to give people something to sing along to. “Do you remember that first time at the Trinity Bar when we played I’m Not Over You, and the crowd started singing back, louder than our little PA could stand?” Churchouse recalls. “All 120 people,” beams Ellard.

The band never expected to get a record deal, says Stride, who, until Scouting For Girls got signed, was working at Carphone Warehouse. “We ran our own mailing list and the Wolf Cubs [their fan club], but there was never any world domination plan – we just wanted to make a living from music.” “It was very much like Only Fools and Horses,” Churchouse says. “You know, ‘This time next year Rodney, we’ll be millionaires!’ ” As it happens, by the time the band had started breaking even, making a couple of hundred quid a month from CDs, they got signed by Epic.

At the bottom of Scouting For Girls’ appeal – and it’s probably the same reason people loathe them – is a sense of optimism and openness. Stride’s attitude is resolutely perky. “I think happiness is a choice,” he says. “Life is relative, you know? The guy who’s in charge of the country is under just as much stress as the woman who’s running the checkout – and sometimes it’s hard but you can choose to be positive when you get up in the morning.”

By the time the lights dim before the show in Bournemouth, the crowd is hysterical. As the band walk on stage the screaming is on a par with a Westlife show. But Stride and co don’t look any fancier on stage than they do in real life; it’s just a former Carphone Warehouse salesman and his two mates. When the band launches into the new single, James Bond, you can’t hear Stride’s voice, such is the mega-decibel singalong it inspires. As a showman, Stride combines the super-entertainer qualities of Robbie Williams with a fun-fair-style charm – to such heady effect that when he requests audience members to give a big kiss to the person next to them, most do.

Back at the pub Stride had said that a big plus of Scouting For Girls’ success was meeting their heroes – Travis, REM and so on – and finding out that they are normal. “Really, they’re three guys or girls who flipped the coin and managed to come up trumps.” By the end of the show tonight, it’s clear from his smiling face that Stride feels himself to be a very lucky man indeed.

For tour dates see www.scoutingforgirls.co.uk. The single James Bond is out now (Epic)

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