Well, I would go for the largest screen you could buy. If you are going to be playing games on it then also try to get one with the lowest response time possible, this stops the games from looking smeared when there is a lot of fast action going on.
Hi nactel, I recently got an Acer 1912 tft from Argos and I've had no problems at all. Its fine with both games and dvd, and its a 19inch screen and was only about �190!! Good luck.
I've got a Viewsonic VX715 - went for quality over size. It's a 17" monitor, but it has the best viewing angle I've seen, and came with a 0% dead pixel policy (instead of the usual tolerance of a few) and 3 years guarantee.
You can get them off the internet for around �180.