Basically I've got given a free S/H PSU This one here http://www.pcper.com/reviews/Cases-and-Cooling/Cooler-Master-iGreen-Power-600Watt-Power-Supply Will it be any use in a new gaming build? And if not is there anything around the £50 mark I should be looking at?
What sort of gaming build are we talking about? As long as you stay within its limits and don't ask it to do silly things, I'm sure it will be fine. However, it is old, and there's a reason why even the top end PSUs only get a 7 year warranty even now. It'll be tired. I'd bung it in a less mission critical rig (HTPC for example) or sell it on eBay and grab a Seasonic, Corsair, Silverstone, be-Quiet or Enermax jobbie around your chosen price point. I will say that if you can stretch another tenner it'll open up your options a little more.
Yeah I have had the same advice from a mate actually. I've just posted a proposed build in the forum http://forums.bit-tech.net/showthread.php?t=266629, so that'll give you an idea of what I'm planning!
It's a bit light on the 12v amps, especially for modern system. I would also advise to get something a bit better, more like at least 20a on each 12v if 3-4 rails, 40a+ if 2 rails.