Thanks for the advice. I took the car for a ride out again this afternoon and gave it yet another blow up the motorway. The wobbly steering wheel is definately just around the 60 to 70 mph region - any slower or faster and it pretty much disappears.
I am now beginning to think the suspension is actually "ok" (I mean not actually faulty)- it's just that my "regular" vehicle is a fairly new Passat and tbh I think I am expecting a 20-year old car to have the same ride quality and sharpness that I take for granted every day......(?) Anyway, I think it would not hurt to give this Quattro some new suspension - as I suspect the existing equipment is indeed original - it must surely be very tired by now, even not having done the big mileage of most cars.
My trusty mechanic has said he will free-off the track rod ends and will arrange to get the tracking set-up properly and I have asked him to check over the transmission for the clunk I have mentioned. What I noticed again today is just how absolutely smooth the engine, clutch and gearbox actually are, so long as I don't jab the accelerator pedal hard while shifting in the lower gears - as that is what causes the clunk and I am pretty certain it is something to do with the transmission at the rear of the car.
A bit of good news in my saga - the speedo needle operated perfectly today.

No fluctuating or stopping altogether, even while batting along at speed. Although the trip and mileage counters are still not moving at all.....

I have burned off about three-quarters of a full petrol tank, so I guess the car has now pegged up about 300-odd miles since it was brought back to legality with Mot and Tax. An oil service and cooling system flush are high on the agenda, along with the all-important cambelt replacement..........
Rather curiously, the engine oil looks almost too clean and someone has overfilled the engine as it is way above the max line on the dipstick... - maybe the former owner did have a heart after all...????
