An electric fuel pump saved her.
I replaced so many things, 2 pumps, push rod, ECU, fuel tank (DO NOT DO THIS UNLESS DEFINITELY NECESSARY as apparently it's impossible to ever get a seal again on the filler pipe entry to the tank, which means there's no feedback pressure to turn off the petrol pump at the garage, so I will forever more have to guess how much I can refuel before it overflows over the forecourt and, if enough fuel is spilt, the fire brigade are called - BEWARE) other bits and pieces. Would have saved a bunch of money and STRESS if I'd gone straight for an electric pump.
A belated thank you to everyone who tried to help and I hope this inspires someone else not to give up. I love my van. Even though, when I told my partner he could use it as a hearse for me when I die, HE suggested it could be buried/burned with me