Cheers for the info.
I checked out the 5850 and it looks good, I've never had an ATi in my life but I've always gone with what I've known.
I toyed with the idea of just the GFX card until I looked back over the compatibility of my current motherboard and it will actually take the Q9400 processor.
So, after some enquiries (luckily, I'm a Systems Engineer, so I deal with a lot of hardware companies) I've managed to find a Q9400 for £133 and an HD5850 for £209 total of £342 ($521).
It's more than my original idea, but I'm guessing it will last me longer, just until after the wedding maybe....