Hah hah - why did I think that might come up? Bit expensive for the casual gamer like me, especially when the desk fan I nabbed from work is doing the trick.
I've ordered a couple more case fans and will stick one in the front to suck air in, and a add another to the one I already have in the back to blow air out - hopefully that will do the trick. I think I'd rather not buy a graphics card cooler (£16/$30) when it may not fit the next card I'd buy.
EDIT:
I was incredibly sceptical, but adding just a couple of case fans did the trick - so for £4 ($8) I've now got a system that functions perfectly - so I strongly advise anyone with similar problems to do the same!
Unecessary background applications can be disabled via the system configuration utility by running "msconfig" under Start Menu - Run.Sometimes it can also help to run a system defrag which will help re-sort data into its appropriate sectors for smoother information processing.