I'm currently looking as well, so I'll share what you can get although I can't offer first hand experience.
For £100 - £140 you can get an Nvidia FX5900XT or a Radeon 9600XT, 9800SE or 9800Pro.
Looking at
http://www.tomshardware.com/ it appears to be between the FX5900XT or a 9800Pro.
Personally I'm waiting for
http://www.microdirect.co.uk/Product...970&GroupID=27 to come back in stock as my budget is nearer £100.
Others will probably have first hand experience of the FX5900XT and 9800Pro