Thanks for all your replies and suggestions, keep them coming!
May well try the Escort and Volvo thing.
Phil, where abouts are you located? I also may be interested in your spares.
Neil. The belching thing happened to me a few years back. I could never find the reason! It used to happen when I was taking long a left hand bend at speed on a slip road, before entering a particular duel carriage way, a quick glance in the mirror showed the smoke, but she never used any oil, sounded fine and never smoked at any other time. The reason I,m looking at the braking system now, is that I have had total brake failure twice...once on the way back from the m.o.t station!
The thing is, this has probably been going on for at least a couple of years and by the amount of fluid in the servo, probably more, possibly with the previous owner I,m aware of how much damage the fluid will do to paintwork, but what about the internals to the servo? I will strip it down at the weekend and have a gander. Can you still buy alcohol at the chemist? Used to use it to clean up my vinyl records,,..remember them?