I made some slight adjustments to your configuration.
Now it is better in every aspect.
Uh, not really. That's what I mean by niggling; it's almost never more than a matter of opinion.
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CPU: same
CPU Cooler: same. I'd suggest the near equivalent Xigmatek Gaia that cools within 1C but is 6db quieter because it's much cheaper in the US, but might not be there; niggling.
Motherboard: MSI Z77A-GD55 ATX LGA1155 Motherboard (£102.32 @ Amazon UK) No. I would NEVER choose MSI over ASRock, especially for overclocking. MSI tends to use weak VRMs that pop under load.
Memory: Patriot Viper 3 8GB (2 x 4GB) DDR3-2133 Memory (£53.40 @ Amazon UK) Not better. I'll take DDR3-1666 CAS9 over DDR3-2133 CAS11 any day. Their performance will be similar, except that the "faster" RAM will default to 1666 speeds but still be CAS11 until you manually tweak it. You'll need to repeat that tweak (or reload saved settings) after any BIOS reset. Why create more work?
Storage: Samsung 840 Series 250GB 2.5" Solid State Disk (£129.98 @ Amazon UK) Maybe. Bigger, but might not be better. The 120GB version of the vanilla 840 was put down pretty hard by HardOCP; the bigger drive should perform better, but the only advantage I see here (which may be sufficient) is its size.
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£45.54 @ Aria PC) Six of one, a half dozen of the other.
Video Card: Asus Radeon HD 7970 3GB Video Card (£320.98 @ Amazon UK) Same card, different brand; my personal experience with Asus video cards has not been good (excellent mobos though), but YMMV.
Case: NZXT Source 210 Elite (Black) ATX Mid Tower Case (£39.95 @ Aria PC). Case is a personal choice item.
Power Supply: XFX 850W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply (£79.99 @ Amazon UK) This is nice, but overkill for one card though; 650W is easily enough.
Optical Drive: Samsung SH-222BB/BEBE DVD/CD Writer (£15.95 @ Amazon UK) Meh. One optical drive is much like another.
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) (£68.39 @ Aria PC) Meh. It is what it is.
Total: £1054.16