I know your 150 limit is strict, but if you wait a few weeks I expect this will drop into price range:

1GB 460 Palit, £155 + free delivery.

http://www.ebuyer.com/product/227182

Budget no frills card, my last couple of cards have been Palit and one was a replacement for a dead Gainward card (same company) and their replacement service was fine (though I was dealing primarily with Scan).

Failing that, Scan have the Asus 768MB version for £122

http://www.scan.co.uk/Products/768MB...2xDL-DVI-mHDMI

But sounds like time is on your side here, so wait for the AMD 6000 series to start popping up and see what it does to prices.