Looks a good buy to me, only real down side is the Intel 945gm 224mb graphics card (but if you don’t want it for gaming it should be good enough).
Don't think more memory will help much (with the graphic card anyway).
Besides if you do
£420 (before or after VAT)?
+£80 for the memory
You are now getting get into the price range where you could do better for a few pounds more.