Well that didn't go very well.
Started the engine and could hear a knock which I had the impression came from the cambelt end near the top. Used the screwdriver in the ear trick to locate where it was coming from without success. The cam sounded like it was working properly along its length. The knock suddenly disappeared after about 10 minutes which I thought was probably due to the engine warming up. I went to the back of the car to check the exhaust outlet, There appeared to be a small amount of white smoke. My initial thought was it was unburnt diesel but it was water vapour confirmed by the liquid in the tail pipe - neighbours gas central heating was on with water vapour evident in the exhaust. Whilst at the rear, the engine suddenly stopped.
Tried to start it again but the starter motor was struggling to turn it over.
All the time there was an exaggerated movement of the engine on its mountings when it was running. Forgot to mention before but during the original incident the four rubber mountings for the top plastic engine cover were ripped from the top of the engine.
Thanks for all your suggestions but I have decided to call it a day.