A superfan’s jaw-dropping collection of Spice Girls memorabilia is to go on a UK tour of 12 cities. It includes costumes, dolls, flasks, lunch boxes, plates, cups, Christmas crackers, toys, biscuits and cushions.

There are also cake toppers, jigsaws, radios, magazines, Easter eggs, Pepsi cans, drinking glasses, handbags, three Aprilia mopeds and dozens of packets of Walkers crisps.

“I’ve always been a bit of a magpie,” said Alan Smith-Allison ahead of the opening of his Spice Girls exhibition in London on Saturday. “I always collected things when I was little.”

The new show features thousands of examples of the multitudinous merchandise that accompanied the band, along with hundreds of costumes the Spice Girls wore for their performances, videos and movie.

The double-decker bus that featured in the Spice World film will arrive and be parked outside the exhibition on Friday, borrowed from a marina on the Isle of Wight and lovingly restored thanks to a crowdfunding campaign.

Visitors will also be able to watch footage from the Spice Girls’ Istanbul concert and, although not compulsory, the whole Spice World movie.

Smith-Allison admits some people might see his obsession as being a little over the top. “I’ve met the two Mels and Geri,” he said. “I would love to meet Victoria and Emma, but at the same time I’m not going to go hang about their houses. I respect their privacy.”

“It’s not about that. This is more of a tribute. I don’t go and hang outside Heart [where Emma Bunton is a DJ] or anything like that.”

Smith-Allison was a teenager when Wannabe came out in 1996 and it changed his world. “In the 90s, being gay and 15-years-old, it was a bit uncomfortable at times. I grew up in Scotland, in a quiet countryside village and it wasn’t always easy.

“I’m not saying ‘oh poor me’ because everybody was in the same boat in the 90s, but these girls came along and said ‘be who you want to be and it doesn’t matter’.”

For girls it was about girl power. For Smith-Alison it was: “If you’re a bit different, a bit quirky then embrace it and go for it, as long as you work hard and try hard you can do whatever you want.”

Smith-Alison was formerly a charity worker, but he realised after buying his first costume in 2007 was that what he really wanted was to build up perhaps the greatest Spice Girls collection in the world and make an exhibition out of it.

It has not been cheap. His partner’s “hair would fall out” if he knew, he said. “It must be well over a hundred grand, probably a couple of hundred.”

Smith-Allison said he had always seen the collection as an investment, and with 10,000 advance tickets already sold for the London show he may be proved right.

There are around 300 costume items in the show, though not arguably the most famous - the union jack dress Geri Halliwell wore at the 1997 Brits, which now resides in the Hard Rock Cafe in Las Vegas. “We asked ... they politely declined,” he said. There are also notably few Baby Spice costumes because Bunton has hung on to them.

The red corset dress with union jack detailing that Halliwell commissioned from Suzanne Neville for the 2012 London Olympics closing ceremony is part of the exhibition on loan from the designer.

After London, the Spice Girls show will move to Manchester and 10 other cities over the next 18 months, Smith-Alison said. Dates are still to be announced.

The band may gone their separate ways, but Smith-Allison said the Spice Girls were still as current today as ever. “Who doesn’t love a bit of fun and girl power and cheesy pop music?”

• The Spice Girl Exhibition is at the Business Design Centre, Islington, from 28 July to 20 August, and at the Manchester Central Convention Complex from 24 August to 4 September