Cheers for all the advice everyone, I'm gonna stick with 2GB of RAM and that RAM is actually pretty cheap so I'm gonna stick with it. I have changed a few things round tho, here's what I have decided to get so far:
I'm ordering from 2 different stores coz of price differences, comes to ~£655.
I want a decent PSU so I can upgrade the graphics card in a year or so without any worries about power consumption and that PSU is competitively priced.
There aren't any compatibility issues from what you guys can see are there?