I personally purchased a Samsung Syncmaster 152V from Office World which was £20 cheaper than anywhere else net included concidering P&P applies for net purchases. Its only a 15" with a response time of 25 M/S which I have not encountered any problems with distortion and it also looks nice mounted on the wall with a bracket I got from Ebay for £29.99 totally satisfied also have NXT speakers which i got from PC world for 19.99 which sets it all off nicely.
Read the reviews certainly, but the best advice I can give is to actually see the monitor working, and judge for yourself.
When I was looking at the end of last year, I found that one highly recommended brand was, (in my opinion), inferior to the one I eventually bought. Admittedly, my main concern was quality of photographs.
You should definitely be able to get a 17" for £350...
I have an LG one they no longer make (model 782 i believe) and it's ace. You'll never go back to CRT!
One thing to note is that TFT's have a 'home' resolution and using it on anything else will make the screen look blurry. Most 15" screens home to 1024x768, most 17" to 1280x1024. If you go into a shop and they show you a 17" running at 1024x768 it will look absolute rubbish but don't be fooled... of course most shops of quality (no comment but *cough* not PCW) will be able to show you what it look like at the 'correct' size.
Sorry if they duplicates anything anyone else has said... i'm at work and I've actually had to do something for the last hour...
Funnily enough... this is the replacement for the one I have (it's "782LE" for the sake of self-correction) - thus highly recommended. I did say £350 would be more than enough... but the below price lasts until Monday at 9am.