Best PSU

Antec, Corsair, XFX, Seasonic, PC Power and Cooling, Cougar, Enermax, OCZ, Xigmatek. Avoid Cooler Master, Thermaltake, Aywun and other cheap brands like they have a contagious disease.  

Though there are high end cooler master power supplies that are pretty good, but those prices are way over 50 euros.

Here is a detailed list with power supplies rated, top tier is the best:
http://www.overclock.net/t/667515/reference-power-suppl...

i ment fifty pounds lol but thanks

I found this one but is 500w enough?
http://www.scan.co.uk/products/500w-corsair-builder-ser...

That is a very good power supply, but technically I need your computer specifications to give you a estimation of how much watts your computer needs. That way we can save money if your computer can run on less than 500 watts.

GIGABYTE WindForce GeForce GTX 660 2GB
Cooler Master CM-690 II Lite Dominator
Intel Core I5-3570 Processor
8GB Mushkin Enhanced BlackLine Frostbyte
Corsair CP-9020047-UK Builder Series
Western Digital Caviar Green 1TB SATA
GIGABYTE GA-Z77-D3H Intel Z77

Yep, that power supply should work without any problems, if you really want to you can scoop down to a 450 watt power supply if you wish to save money. A estimation of how much watts your build uses would be around 300-350 watts. Though you should always try to get above the consumed wattage just to be on the safe side, 450 watts is enough for this build and future upgrades. I included a DVD drive in your build since it does use around 30 watts at load. No fans were included but they are pretty minimal when it comes to a power supply.

the case comes with two fans

Yep that does not really affect the power supply, I mean at most that adds around 10 watts.