Update - decided that one of the New Year's Resolution was to fix it (finally! )
Had a look under at the lower mounting - it looked OK, but found that I could move the bottom part of the rubber against the metal shell, so out it came.
None of the rubber was bonded to the metal at all; it hadn;t been for a while, judging by the rust on the rubber.
Good job, as I had to get a hacksaw in to get the shell out.
With it off, the engine seemed a tad wobbly; the other two mountings are probably soft now - job for Spring.
There is only the tiniest vibration that you can see on the gearstick, but cannot feel or hear now if you floor it - I can live with that.
Funny vibration on ZX TD - got me baffled at present!
Moderator: RichardW