Boys this is the Aeroforum? Handbags and sharp fingers nails belong in pub after a few.
Having said that I do remember a youtoob video on Superform and mentioning it being on the outskirts of Birmingham. Damn, there I go joining in.
Anyway back to the main subject.
I remember a number of times when it all appeared to be good but the car would not start. IIRC the ground path for the starter motor can also be part of the issue? If it cannot make full current it will fail to turn? Given the other things mentioned I don't think it is the issue but might be worth checking as well.
Given the AeroMax was around the same time as the Series 4 it would be good to try and get a Max or a 4 nearby in order to perform a side-by-side. If it helps I could bring the Coupe but that is 2013 so who knows how the gremlins moved things about in the intervening period?