I've not heard anyone having trouble doing it last year. Indeed the FAQ page specifically said it was possible! In fact, look at this, I've just found the screenshot I took last year...Nice, I may look into reserving one via iUP and then buying it outright, but I don't want to spend £10 on a 1.5 hour coach ride to London + £2-3 on Tube to visit the Apple Store in London (as there is no Apple Store in Oxford), only to be told I can't buy it outright and have to get it on iUP, so I am looking for confirmation. If you say Regent Street did that for you, then I'll try getting one from there.

It could be different this year though.