Weird screen fault

Solution 1:

As I can see from your profile: You live in the UK. How's the winter this year? I mean: How cold is it? And how are you carrying your iPhone around? Inside your trouser's pocket? Or inside your coat's pocket? So yeah, maybe it sufferd from extreme differences in temperature plus condensation.

Solution 2:

I would say from the cloudiness around the edges of your screen it looks like water damage and the fact that there are water droplets (or appear to be) on the phone in the pictures I would check the water sensors very closely (in the headphone jack and in the charge port) if they are even the slightest color of pink your probably not going to have much luck at the Apple store unless you get real lucky and get a newbe at the Genius Bar. Good luck with it though.