I'm not sure how much a Lumia 920 is in the UK at the moment but I know it must be cheaper than at launch. However, I want to buy a Surface Pro 3 for my 6th form education, and am already saving for it.
The 920 is definitely a lot cheaper than at launch. The best place to pick one up here in the UK is at Tesco for just ?199 Sim Free (unlocked).
However I'd have to agree with Andrew that the Surface Pro 3, especially for your 6th form education, would be the best one to save up for if you can do it. I'd have loved one of those when I was in 6th form
I've found one for ?137 (an absolute bargain considering my 520 was ?100).
How much does a 520 sell for these days, because im ?300 from a Surface Pro 3 intel i5 128gb model, and I could buy the Lumia 920 today if I wanted.