SamuelCB:
Brilliant thanks, so if I need 5amps I should go for maybe 5.5-6amps to cover possible loss?
Well everyone has their own comfort level on how much extra 'headroom' they wish to have when they looking to purchase a power supply. As more current capacity also usually means larger volume, it's a trade-off type decision. I like 25%-50% extra current capacity so I would be looking for say 6 to 8 range for a 5 amp continuous load. Have you considered using a PC power supply as they are very cheap (usually free from salvaging old PCs) and have lots of 12vdc current capacity?
Lefty