Thanks for you fast response, so a few things to think about
ill get a multimeter on an old power supply and just have a look at the step down transformer voltage, you never know 12 volt?
stability of the battery could maybe be sorted with a second battery and some split charging switch or something similar
Dig out a really old motherboard to test the thing on
Would a better solution be to use an inverter to go back to 240v first?
I guess the best solution would be to get hold of a laptop, but i never was one for easy solutions... Thanks again