2 options from Sony below:
1. SONY BRAVIA KDL42W705BBU
Curry's £429.00
Review
One of the lowest input lag readings HDTV test ever recorded, downsides are no 3d, no Motion Flow settings for fast moving TV e.g. football and onlly 200 Hz processing rate (although the review said it seems to handle football good enough)
Should be perfect for Gaming
2. SONY BRAVIA KDL42W829BBU
Curry's £499.00
Review
This is a higher spec model than number 1, has 3D, has motionflow options, has a 400 Hz processing rate and also has really low Input Lag. Only downside is that it is £50 out of your budget. But if you shop around i'm sure you could knock a few £££ off it e.g.
Appliances Direct £459.98
Direct TVs £459.98
I have this very TV only the 55" model and found it perfect for gaming on my Xbox One. 1 thing to note about number 2 is that the review seems to recommend going for at least the 50" version Quote "which is equipped with blur-busting motion interpolation technology."