and i5 750 is good, but it's not the only cpu that's good for gaming.
if you were to switch some parts around to go the amd route, you could get pretty much the same gaming performance at a lower cost.
AMD Phenom II X4 955 Black Edition Socket AM3 3.2 GHz.. | Ebuyer.com
Asus M4A87TD/USB3 870 Socket AM3 8 Channel Audio ATX.. | Ebuyer.com
those changes would save you a little over £40.
and just skip that gfx card. they are charging you extra just because it comes slightly factory OC'ed (something you can very easily do yourself). get this one,
MSI GTX 460 Cyclone OC Edition 768MB GDDR5 Dual DVI.. | Ebuyer.com
it's the cheapest one available, a little over £20 cheaper, and this will perform just as well. actually, it should be a tad better since this one also happens to be a pre OC'ed card, and is actually clocked higher than the gigabyte (doesn't really matter though since you can OC it much higher yourself, just a bonus i guess).
something else you could change, not necessarily to save money;
for just over £3 more, i would grab this kit instead,
OCZ 4GB (2x2GB) DDR3 1333MHz/PC3-10666 Platinum i5.. | Ebuyer.com
rated at tighter timings.
or you could grab this kit for £14 more,
Corsair 4GB (2x2GB) DDR3 1600MHz XMS3 Memory Kit.. | Ebuyer.com
rated at both a higher speed and tighter timings.