Still got the problem unfortunately.
I’ve had the ecu out, checked for water ingress, non showing, pins all ok but I cleaned them anyway with deoxit (I use this on my hifi kit) and dusted with wd40 just in case.
I’ve had the road speed sensor off, emery clothed the chassis and the Just nut on the bolt to make sure it’s a good ground, wd40 too.
The car is fine until I put it down a long steep downhill and then stop at the bottom, and there it stops.
I read somewhere that low oil pressure can knock out the fuel pump, I tried watching the pressure tonight but it didn’t give me an obvious reading to confirm a big drop.
Frustrating, but at the same time entertaining trying to find the cause.