That budget is a bit tight for a 'fast' pc.
Cheapest pc at ebuyer with AMD, that fits your remit is
http://www.ebuyer.com/274483-hp-pro-3305-mt-desktop-lh050ea-abu
only 3gb of ram, but easily expandable
Any reason for wanting an AMD ?
The best PC's i've had have all been AMD, Had an intel PC once and it was terrible.
Currently got 4GB Ram in my current PC, bout month ago i had a problem with my PC, then it worked fine for maybe a week, and since then it's slow as hell, takes like a minute just to load up a webpage.
Sky Blue Up North - i use to work near Eclipse, but i've only heard bad things about them, how they try to pass off refurb stuff as brand new. I wouldn't like to do it myself anyway, i have a rough idea of the bits and bobs, but i know it would take me ageas and i would get frustrated with it and just end up chucking it after being sat in my attic for a few years half built.
I've heard of Dabs, but forgot about them, will have a look,
Thanks everyone for the suggestions.