Update on this, had the car out today and managed to reproduce the problem.
Its not related to hills, so its not crap in the tank, but rather using sustained full power. All signs point to inadequate fuel pressure.
I was overtaking a small van and mid-way through the manuevure the car started to miss, just as before, and eventually got so bad I had to pull over. I finally got the car running again by cranking multiple times with full throttle, this must get the pressure back up in the mechanical pump and eventually it was back to normal.
I think we need to issue a caution on these newer Bosch pumps until we can be really sure they are ok
