Are you in desperate need of a nexus 4?
Just browsing the o2 website and happened to come across this:
So if anybody is that desperate for a nexus 4 in the UK then this might be the way you have to go!
Although saying that, while I'm aware you will eventually be able to get for £280 from the play store considering carphone warehouse has the gs3 for £519 on Pay as you go and the Galaxy note (different league of device i know) for £549 sim only it isn't the worst deal in the world!
Personally i would just wait it out but i know there are probably a few people who want the latest nexus device!