title says it all, what do i want to see in a £100-140 screen taht shows its good? response time? resolution? contrast ratio? anyone know?

Are you gaming I am guessing?  Response time is a big one.  I think they say you should have 5 ms or better, but the lower that number, the better.  

Also... higher contrast ratios... though be careful some are actual and some are not. You want to know the native resolution... that's the size it will best work at (what it was built to display)... anything bigger and it can look sotchy and anything smaller and it can look squished. Also, get something with a decent warranty and from a reputable name. Also, make sure if your using DVI that it has cables included or whether need to purchase... some do and some don't. Same thing id going to analog way... as some do have DVI cables only.