I had the same problems last year as you. Actually, the engine would cut out at random times, ( not good when on the slip roads to roundabouts!) and wouldn't start for 10 minutes or so.
After changing the fuel pump, and the injector wiring loom due to seal failure allowing oil to creep into the ECM connector I thought it cured the problem.
It turned out to be the air bleed valve was blocked, it wouldn't allow air to vent back to the tank.
I got a replacement bleed valve from John Craddock and there's been no problems starting and running the engine since.
If you do decide to replace it, it's in the outer rear hose to the fuel filter, and be very careful as the threads will most likely be corroded and stiff, very easy to break off.https://www.johncraddockltd.co.uk/wjn50 ... ilter.html