I have just bought an ATI Sapphire 9250 128mb PCI card for my PC (doesn't have an AGP slot). I couldn't justify spending nearly

For cooling, I'd look at the range of Zalman GFX cooling solutions. QuietPC stock them. I think you need the ZM80D-HP for your card.

It's about

Brilliant, how much can you overclock by with one of these beauties?

They Dont overclock too far on the memory but can be pushed quite hard on on the Core Speed, I used to have a 9200SE (Which Is Outperformed by 4 year old 8500!!) and overclocked it alot, Given it's limited bandwith, you'll notice hardly any difference.