well the x1950pro is around the £100 range...and with that u can almost max out cod2 and fear (90 here: http://www.ebuyer.com/UK/product/119203).
I think the x1950GT is slightly cheaper around the 85 range (but more power hungry and not as good, but good enough). 7900GS by nvidia is also around the 70-100 range and just as good. (found one for 75: http://www.ebuyer.com/UK/product/121108)
if not then the there is always the 1650XT, or 7600GT
all of this depends on your psu aswell though. so let us know what ur psu is.