This a cracking power supply for the price. For £68 you get a very good quality seasonic made psu. It is capable of running two high end cards in crossfire/sli.
XFX Core Edition PRO850W - power supply - 850 Watt
Power supply - active Power Factor Correction (PFC) - internal
ATX12V 2.2/ EPS12V 2.91
+3.3, +5, ±12 V
1 x power 24 pin ATX with detachable 4 pin section , 1 x power 8 pin EPS12V with detachable 4 pin ATX12V section , 2 x 6 pin PCI Express power , 2 x 8 pin PCI Express power with detachable 2 pin section , 11 x 15 pin Serial ATA power , 7 x 4 PIN internal power , 1 x 4 PIN mini-power connector
140 mm fan
ENERGY STAR Qualified
5 years warranty
This is priced at around £80 in other shops. The only downside is that it is not modular.
Here's a review for it http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=217