I currently use the Sapphire 6850. I bought it in September '12 and it's been OC'ed 24/7 since September '12. It's a great card (sorry for your bad luck sam_p_lay) that hasn't let me down. It's starting to show it's age in games like FC3 & BF3 and will probably be "obsolete" once the new Radeons / GTX's release this year.
If I'm not mistaken, £75 is around $122 USD. That's way overpriced considering brand new they're $130-$150. For that price you could get a new Radeon 7770 and be just as happy.
Edit: Just noticed your resolution, the 7770 should be able to max out any game at your resolution. Not to mention they overclock quite nicely netting you an extra 2-3 FPS. You should definitely get a new PSU too. Protect your invest and don't skimp on the quality.