Hi Greg Sorry for long time between my responses. It was not really practicle for me to try your suggestion on the road in a broken down situation as to access filter I have to remove one of the batteries etc.
However problem is now solved. It turns out that the problem is the Fuel Pump itself. After all it is nearly 20 years old. The rubber seals in the pump go hard over the years and especially when cold air will seep into the pump. It causes all the same problems as above. Worse it also allowed the main drive shaft into the pump to let deisel fuel into the engine oil and vice versa. I took the car to Auto Marine deisel fuel pump specialists in Hove for them to completelty overhaul the pump. A bit expensive but well worth it. All running problems have now gone 2 months on and engine once, oil removed, flushed and replaced with new oil is purring better than ever with more power. Thanks for you help, but it needed a bit more than me tinkering with it. Hope this post helps anyone else out there with the same issues. Cheers Felix