What about a soundcard and surround speakers?

 

Normally I see a system for this sort of budget with no upgrade potential, you however are the exception so kudos.
You will be hard pushed to find any to disparage the core2 line although that motherboard does not sport the 1333MHz fronside bus of the processor. Alas a "weaker" processor will probably cost you more so a motherboard upgrade it is.
Perhaps something like this:
http://www.overclockers.co.uk/showproduct....catid=5&subcat=
HDD: A 320GByte will do OK but for the few pounds extra you might as well go for the 500.

Do as noamkot says and spring for a decent PSU as well.

 

Agreed. 8600GT's are now 100$ USD(not sure what that is in funny money)

 

A case/PSU will likely set you back another £100 if you want to do it properly. If you have a case that will work (atx has been around for a while) I would say do that now and grab another a month or two after, if it is a really cheap case with minimal air flow then leave off overclocking and such until it is replaced.

Many of us around here ended up with an Antec 900 gamers case and I can safely suggest that:
http://www.overclockers.co.uk/showproduct....rodid=CA-065-AN
It is a shade on the expensive side though.

As for power you do not seem interested in crossfire/SLI, a big RAID and so forth so you can probably afford a lower power output (which will have to be upgraded when the time comes if you want to add such things). A decent one is a must though still.
I am hesitant to speculate on a wattage (500W should do but I am unsure if you will get away with lower (those 8xxx cards are fairly power hungry and overclocking cooling also ups power requirements).
Around £50 incl VAT should net you a good one.
http://www.overclockers.co.uk/productlist....atid=123&rows=0

As for graphics, dx10 for me does not enthuse (and cheap DX10 cards even more so) and in the 9 months until something absolutely requires it (let alone something that is a long tech demo) then yeah.

 

If you want to go under budget try and find someone with a business and get them to order it, VAT is around £75 on that. You will not see the cash for a little while (3 months is the tax period as I recall) but yeah.

PC building is square peg in square peg hole sort of thing and it comes with manuals to do it (if you do not read said manual you are asking for trouble). The most important part I find is to get the drivers (bundled stuff is usually old and bug ridden), OS and stuff to install all sorted beforehand (there are a few threads recently linking peoples choice apps up one here: http://gbatemp.net/index.php?showtopic=54757&hl= ).
The only real things to make sure of are:
USB and firewire often have the same connectors (different colours or names by them though) on the motherboard: do not confuse them. Likewise the power button to the board may also be slightly confusing.
Graphics cards and motherboards tend to have two power inputs: unless the manual says otherwise (and I know of none that do) power all of them.
Loose connections are a pain, avoid them.
CPU + heatsink. The core2 line come with decent coolers but adding them can be a pain: there are several stripes of conductive paste already applied and the force of attaching the fan is supposed to spread it out. Make sure to be careful when applying this unless you want to go and buy some more (which is fairly expensive).

PSU: akasa do great PSUs (I have used them in a few builds recently and that one should work fine.
Case: I would happily give you a case (presently we are in the same town it would seem) but I am not sure I have a spare ATX one around. You can probably bring yourself into budget with a trip into town but most of those deals are junk case+PSU bundles.

All other components should work fine together.

I assume also you have a CD/DVD drive, keyboard mouse etc already.

Edit:
Missed the speakers etc.

This sort of stuff ideally gets factored in but most (myself included) leave it out of for friends/family members to get for "tech gifts". Not to mention each adds a

Mouse: laser, USB and wired is my choice. Gamers mice are not bad but are often horrendously overpriced.
Keyboard: I am suffering a £5 keyboard presently, no model numbers or anything I can suggest.
Speakers: good speakers are more than you will spend on this machine and also make a good upgrade, stick with some standard stereo stuff or even use the ones from your stereo (search for a 3.5 mm jack to RCA/phono). http://www.cableuniverse.co.uk should do them and I know there are places in town that do them for less than £10.

 

Seriously thanks for the help, going to order the stuff tonight. Will also post some pictures when I have finished building, thanks!

 

personaly I would go down a few cpu's, and use the 10-20pounds saved to buy a decent 5.1 sound card

Alot of modern games are raped by onboard sound, u will loose fps from processing too many noises
pretty much any game after 2005, has this problem