Thanks all for your info and ideas, appreciate you taking the time.
Made a bit of progress today....
Removed and tested the servo, it nulls itself on applying 12v to the plug. Good news!
Bit of a bugger getting it in and out but hopefully won't need to do that again.
There was no eliminator fitted, just normal loom plug.
I guess as long as servo sits at null, regardless if cables are not connected, then it won't throw up the 7k rpm code.
I did try ignition on with plug disconnected and did get 7k rpm code.
I think I've managed to source a working valve assy with pulley at a reasonable price just need to order it.
So hopefully in the next for weeks I may have a functional exup 🤞