BabyGeezer:
Okay, looks like i'll be going with that option - how about the current, those converters will pass the input supply current through with no losses ?
It doesn't work like that. The short answer is don't worry, it will do what you need.
A DC DC converter swaps current for voltage. If you feed 12V in and take 5V out at 1A then the input current at 12V will be a lot less. If there were no losses then the input current at 12V for 5V 1A out would be 5/12 * 1 = 0.42A (This is where some kind person tells me I got the maths wrong!) However, they are not perfect, they do waste some power so I would assume that for 1A out at 5V then 0.5A in at 12V would be needed.
Just connect it up, it will be OK.