Looking for a psu for under £50. Cheaper the better if possible.

So far im looking at these...

OCZ 600W StealthXStream 2

http://www.currys.co.uk/gbuk/ocz-600w-stealthxstre...

CORSAIR Gaming Series GS600 600W

http://www.currys.co.uk/gbuk/corsair-gaming-series...

Heard corsair are the best. So should i go with the corsair one? If so, why? Anything apart from the brand name?

Thanks. Im up for anymore recommendations. But my budget ends at £50 im afraid.

Its for a 6850 + i5 2500 build