If I may make a suggestion...

PC hardware changes constantly. Unless you like to spend money, never buy 1st tier (stuff that has just been released). For example - in NA, video cards have always come out at around $600. This has been going on for 20 years. That $600 vidcard will be a $300 vidcard in 4-6 months. Buy 2nd tier (stuff that has been out 6months to a year). Don't try to future-proof.

Besides, you'll get a ton of PC for your budget, and money left over for beer.

Thank You... Great advise here...

Could You be so kind as to suggest a possible rig for me to start researching?..
I think i might find a breakdown of a complete list of components recommended by You Guy's really helpful. minus monitor/keyboard etc.. I have been looking at custom configuration sites but i am finding the choices and compatibility a little overwhelming...

Thank You...

OK, here's an example. I used the Overclockers UK catalog. I don't know UK vendors really well, but others have told me they're reliable. This covers the case and everything that goes in it, not mouse, keyboard, speakers, headset, or monitor.

CPU: Intel Core i5 2500 £158 (comes with a cooler, just use that unless you overclock)
Motherboard: Gigabyte P67A-UD3-B3 £115 (the onboard sound is not great, but OK)
RAM: G.Skill Ripjaws 2x2GB £40 (you can get DDR3-1333 CAS 8 or DDR3-1600 CAS 9)
Graphics card: Either XFX HD 6950 or ASUS GTX 560 Ti, they're both £174; I would favor the 560 Ti
Hard disk: WD Caviar Black 1TB £69
DVD drive: Samsung SH-S222AB £17 (DVD drives wear out; don't overspend)
Case: CoolerMaster HAF 912 Plus £60
Power Supply: Antec "High Current Gamer" 620W £50 (same as the very good Seasonic M12II; this isn't a Delta-made unit)
Windows 7 Home Premium x64 OEM £80
Arctic Cooling MX-4 Thermal Compound £7 (I like this better than Arctic Silver 5, which Overclockers doesn't carry anyway)

Total £770

To squish a few more £ you might want to have a look at Phenom II X4 equivalents. AMD are no match for Intel at the top of the range, but in your budget they provide very good perf/price ratio, particularly when you consider the price of CPU+MOBO instead of CPU alone (AM3 MOBOs tend to be cheaper than the ones you need for Core i5). Remember that on a gaming PC you'll want to be cheaper on the CPU and spend more on the GPU... within reasonable limits, of course. You might also want to get a little bit more RAM, too: in my experience, 4 GiB isn't enough in Windows 7 if you want to get rid of the swap file. Even on my laptop I have 8 GiB.

They're not made for gaming, but that doesn't mean it won't work. It depends entirely on the demands of the game, of course. The latest graphics churning monster game (which might be what the Witcher 2 is) won't work well on an average laptop, but less demanding games (like many strategy games) work very well. And I played Vampire Bloodlines entirely on a mediocre Dell laptop. Even at low settings, TW2 is pretty spectacular.

I moderate a forum and we get requests all the time about a build. As was stated, we ask two questions, what are you planning to use it for and what is your budget? Once we have that information, we go shopping and list the parts and links ( usually from the same place ) . I have done several from the UK and usually use the PC World Superstore over there.