I have a budget of about £90 I originally opted for the GeForce 9800GT but someone recommended the ATI 4850 or 4770. This is the first computer that I have built and I am a total n00b. Which of these graphics cards would you recommend?
4850 > 4770 > 9800 in terms of pure performance.
If they all cost the same however I would probably go for the HD4770 as its smaller, cooler and more power efficient. But they are usually hard to find and more expensive when you do so.
In other words get the HD4850.
Nothing I could suggest would fit your budget of £90.
Make sure you have a look at a similar display first though. It is not gonig to be terrible by any means, but many people find issues in the image quality of a lower end LCD. This won't be much of a concern if you already have an LCD, but might be if you are moving from a CRT.
I'd go for an 19" monitor at the least. They aren't much more. Or this 20" is £79.51 http://www.dabs.com/products/best-value-20--jt209rp-ws-...
Surely the extra 3 inches are worth £10.
Honestly I don't know much about picking out a good cheap monitor at the moment. Perhaps someone else can give you better advice in that area.
The HD4850 1gig is the right choice for any of these monitors btw.