Just ordered one of these. (see Link)
http://www.ebay.co.uk/itm/12V-30A-36...item564ebe30df
30A 12V PSU for less than 20quid.
I know you can use old computer PSU but seems a bit too much messing about. When this arrives will put it into a box, a flex lead and plug for mains and couple of banana sockets for Vout, job done.
Thought I would post as it maybe of intrest to someone.