For that motherboard and GPU combination, your looking at about 130w.
So if you add cpu, memory, HDD, DVD, card readers etc etc
You could get away with a Super Flower Golden Green HX 350W 80+Gold 350w £47.99
If you want plan to upgrade in the future, Super Flower Golden Green HX 550W 80+Gold 550w £61
I trust Superflower enough to power my own server with the above 350w model.