I didn't even know there was a 128mb 9800 XT... I was going to say whatever you do go with ATI for HL2. That's my opinion at least, I guess we will see the actual numbers when the game gets closer to release.
Three step guide to good HL2 and a place for your soul in Nirvana:
1. Buy Radeon X800 XT.
2. Buy a box.
3. Place your newly bought X800 in the box, add stamps, and then mail it to me.
That'd be fine, assuming your not overpaying (which I don't think you are, I don't remember conversions for pounds). Just keep in mind (I get the feeling you don't realize this) that more memory doesn't mean a faster card (a Radeon 9600 256MB is hella slow).
The 9800 Pro is a great card... Just shop around first. If that's the lowest you can find it for, compare its prices to, say, the GeForce 6800 128MB. If the 6800 128MB is ~$400 or more (converted) I would go with the 9800 Pro.
well, that's what he told me...a friend of his father can get him a R9800XT for only 200$... a new one!! I'll ask him again just to make sure its the XT and not PRO