After being scrapped by Channel 4 and revived by Five, the Big Brother bandwagon rolled into Glasgow yesterday with the show's Endemol production team claiming they are ready to reconquer the ratings charts with a little help from Scotland.

The first outing of Big Brother on Five last year tanked in the ratings. Many felt that was down to the producers failing to come north. None of the housemates were from Scotland, Wales or Northern Ireland. This year, producers are aware they need more diversity.

It's 13 years since the first Big Brother aired and, love it or hate it, the reality show changed the face of TV. For the first series nearly seven million viewers tuned in to catch Nasty Nick Bateman's humiliation. The show's appeal withered, though, to an average of two million. Last year's rating averaged 1.7 million.

So with financial pressure on Endemol, which last year had to negotiate its £2.3 billion debt with shareholders, and ratings pressure on Five, the heat is on for Big Brother to deliver this time round.

Down at the SECC where auditions were being held, producers for the programme insisted they do not set out with a cast list for housemates. But the first airing of the show on Five last year saw a houseful of nubile, all-English and very bland 20-somethings which failed to appeal to UK viewers.

"We don't set out with an idea for what kind of housemates we'd like. That would be dangerous," said executive producer Katy Smith.

"Last year we were very pushed for time and we didn't come to Scotland, which was a mistake. Channel 5 had asked for a dynamic mix of young and attractive housemates, though that's as far as the instructions went, and that's what we gave them. This year we want a wide variety of characters – as wide as possible. Big Brother is extremely important to Channel 5 and they are relying on us to make this series the best it possibly can be."

In previous years big characters and big shocks have proved the draw for viewers: from Jade Goody's permanent foot-in-mouth to transgender Nadia; from anorexic Nikki to Kinga's notorious sex act.

The most recent Celebrity Big Brother proved the brand wasn't dead. It was a hit with unlikely bedfellows Michael Madsen, Frankie Cocozza and Ryan Giggs's former sister-in-law Natasha.

The two-hour series opener, the second to air on Channel 5, was watched by 3.5million viewers – a 15.9% share of the audience.

Denise Welsh's increasingly bizarre behaviour, Playboy models and twins Kristina and Karissa Shannon and ex-Eastender Natalie Cassidy helped reap high ratings for the show, which producers hope will spill over to the forthcoming series.

Buying Big Brother from Channel 4 in its 11th year was a risky move for Five, the results of which will only become clear now that the show has had a chance to bed in with its new broadcaster. Late last year Endemol reached an agreement with the majority of its lenders to restructure a €2.8bn (£2.3) debt load, putting extra pressure on the show to deliver.

Producers have said, somewhat predictably, that this year will build on and consolidate Big Brother's place as Five's flagship show. "The characters are the thing," added Jamie Sutcliffe, the show's producer. "W e have some surprises lined up, of course, but it all hangs on finding people the viewers want to watch.

"We are trying to make it as varied as possible this year as last year was fairly London-centric and a fairly young group. We've learned from that. Celebrity Big Brother was a huge success and now we're focusing on building on and consolidating that success by keeping the viewers who tuned in for that."

Jamie East, presenter of the show's spin-off series Big Brother's Bit On The Side, was also in Glasgow filming a behind the scenes look at the "journey" of select would-be housemates.

"There will be at least one older housemate this year," he said. "We have a big twist coming up but what I can say is there will definitely be someone older in the house. It will be more mixed than last year and yes, people will be tuning in."