EN48 - Thanks, thats exactly what I was looking for, but couldn't find
Chi Sin Gei Si - Thanks, but i'm not trying to turn in to AC, which is what the inverter would, as mfriskel said i'm trying to step down DC from 24v - 12v
mfriskel - Thats what I kept coming acorss, but wanted something rather less permanent to do the job that I could move between aircraft.
Thanks all, EN48 has hit the nail on the head