Apple iPadThe Apple iPad officially goes on sale in the UK at 8am tomorrow, 28 May, however some pre-order units of the touchscreen, tablet-style computer have been delivered a day early.

On Twitter, people have been celebrating the early arrival of their iPad. "Bit of breaking news for you. UPS just delivered my colleagues iPad, one day early!" wrote Twitter user, Jamie Bishop (@).

Also on Twitter, Will Sheward wrote: "My iPad has just arrived (1 day early). UPS delivery guy says he's delivering lots today. I get the impression his van is full of them."

Brian in London tweeted: "iPad is here in the UK, a day early. UPS guy said they've delivered about 700 so far. Nice size. Feels solid."

Meanwhile Apple fans have started queueing overnight outside the Apple store on London's Regent street. The Sun reports that some Apple fans have paid hundreds of pounds for hired shoppers to wait overnight in the line.

Apple iPad

More than 100 branches of Currys and PC World will also be stocking Apple iPad, and stock will be sold on a first-come, first-served basis.

But Brian Trevaskiss of online retailer More Computers has warned consumers to be wary of purchasing the Apple iPad from unscrupulous web stores.

Trevaskiss told Techworld's sister publication PC Advisor that legitimate online stores currently have no iPads to sell, and no way of knowing when Apple will free up the supply chain. He added that customers shouldn't trust stores if they claim to have iPads 'in stock'.

As a consequence, Trevaskiss believes that iPad purchasers could face a long wait if they part with their money at the wrong place, but there's no suggestion that any stores would fail to fulfill the sale in the end.

"Like a lot of people we're keen to get our hands on Apple's iPads, but the truth is none of the reputable UK distributors have any stock or can even give any indication as to when stock might be available," Trevaskiss said. "If you see an iPad online 'in stock', I'd be very wary."

It is however possible that retailers could source iPads from the US, of course, but this should be made clear at the point of purchase.

Matt Egan at PC Advisor contributed to this article.