I'd go with a Core 2 Duo rather than AMD, since they are the best thats out right now, and extremely overclockable. You could buy the entry level (around 190 dollar U.S) core 2 duo that you could overclock to perform as well as a Core 2 Extreme, which would blow away that AMD you're looking at.
So, if you do go that route you would obviously have to pick out a new mobo.
I am not sure how much 382 pounds is in american, do you? That would help.
If you don't, I'd go with a 500 watt PSU. Here is a good one:
Hope this helps. Can you list the ram you have chosen in more detail? I.e. bus speed, etc