Update ..... I've rooted the Huawei tablet but spent ages trying to access the bootloader, which, surprise, is locked. This tablet is one of the hardest to fiddle with, so I've asked Huawei for the unlock code. maybe they will send it.
All I'm trying to do is run a script that tells the tablet to start regardless of the power on state and even if its battery is dead and it has switched itself off.
Alternative is to drill a hole in the dash and fit a pin of some sort to push the power button... no thanks!