OK, after yesterday I can add 2 things. My theory that the engine did not cut out when revved is not correct. I wedged the throttle butterfly with a cable tie so that the engine maintained about 1500 rpm and it still cut out after about 40 mins running. After it had cut, I removed the king lead from the distributor, held it about 5 mm from ground and cranked the engine, loads of spark. Whilst engine was cranking, I put the lead back into the distributor and engine started and ran, very lumpy, would not rev, cut out again. Left the car for about 30 mins, started up again fine. I am going to change the fuel pump and pressure regulator I think. After all, they are 27 years old and that would eliminate the fuel delivery side of things.