Are you keeping the ,monitor, keyboard etc? I'll assume u are for the moment.
Either the AMD Phenom II x2 550 or Athlon II X3 (440 I suppose) in the $80 range would be good
AMD 880G or 785G in the $80 range
4 gigs DDR3 ram-$100
ATI HD5770- $150
Samsung F3 hard drive or a nice 2 GB would be great. ~$100-130
?? Not sure what else you'd need
GDDR5 is pretty much standard for high end graphics cards these days. DDR3 was (probably still is) used on graphics cards, which is as far as I know virtually identical to the DDR3 used as system memory. GDDR5 is a revision specifically for graphics cards. For graphics cards GDDR5 is better, but comparing it to DDR3 is most of the time like comparing apples to oranges.
Don't get the 965 as it is a factory OC-ed 955, it is exceedingly simple to get 965-like performance out of a 955, and even if you don't do that the (typical) price difference between them is not justifiable. I think the upgrade to a 955 probably would be worth it, as it's pretty powerful and the extra £30 would pay for itself in the delay between needing to upgrade compared to getting a dual or tri core.
For a gaming build it is highly unlikely that you will ever need 8GB of RAM. And when you would have done, it would have been better to actually get it at that time, as I doubt it will come in the useful lifetime of that build. Everything else is fine tho, altho again you probably could have improved the build elsewhere if you hadn't 'wasted' money on 8GB of RAM.