for gfx cards the manufactures of the cards dont really matter
. Most go by the reference design of the gpu manufacturer. Go with the one that is cheapest/has best offer (warranty, included games,...) for you.
As for the card itself. Go to whatever shop you use in the uk, put in you max price and get the best card you can afford (go with most memory, newest gpu,...) You might want to look into the VGA charts here on THG.
if you are lucky you might get a 6800 (like here on newegg for under 180$ + shipping
Sorry that i cant say anything else useful