Thank you very much for the advice on this thus far.
Regarding the medical side, I am aware I would almost certainly need to go and see an autism specialist before a medical certificate was issued. From what I have read on the CAA and CASA guidance pages they generally base a decision on biographical history/appearance amongst a few other things. From the research I've done I haven't got any history that would raise alarm bells so to speak but I can never be sure of a pass until I go for a medical.
Regarding minimum time, I think I may have been a bit confused with BA. From what I'm aware quite a few others have placed limits in the past, I would imagine many airlines would look at people on a case-by-case basis. With the MPL (though I'm aware that the FPP is still fATPL) becoming more popular I can imagine that the airlines are looking to train people differently to the older methods and there may be fears that lots of solo SEP time may breed "bad" habits.
The recommended approach to West Atlantic seems a good one, I did see on Pilot Jobs Network that for the 2012 intake they appeared to prefer folk under 26, though that appears to have been removed for the 2013 intake, hence I was initially a little concerned about the age side.
Good news is that I reckon I've got a 10-15 year window to consider each scheme as it becomes available. Plenty could change in that time (5 years ago I'd never have dreamt of BA securing loans). I'll try and get into a position which will allow me to start applications in the next year or so. Will potentially look to glide in the meantime for fun.