Many thanks for all the tips and suggestions folks.
I have noticed that the idler wheel isn't running absolutely true, so that is probably the source of the wow.
Now that I have moved to the alternative system I had to lash something up to play the MC cartridge through, before building one of my splendid valve preamps.
I knew that I had a head amp pcb in the 'junk' box, one that I think I must have had for 30 years
Don't let on but it uses (say it quietly) transistors. I must have experimented a long while ago with using it as a single channel microphone preamp because when I lashed it up one channel had 10 times the gain of the other
Anyhow I've now boxed it up and it makes a respectable noise with my new MC cart.
PCB looks like this:
It's battery powered from a 9V battery, but does need careful positioning to reduce hum pick-up to a minimum. Internals shot:
So far so good,
Alan