Thanks Guys.
I'm more of a mechanical chap than electronics...

The wiring and circuitry has always been my toughest part of this project. So, before you tell me I have deserved this...
my earthing and shielding is, ..well lets just say.... "inadequate"

My power lines are (more by luck than judgement) away from the signal wires but the earthing is only through what gets provided via the 3 pin plugs used - nothing more than that occurred to me - sorry.

To improve my position, what is the proper way to earth a system like this and how best should I shield things?
Many thanks for your help - sorry I set myself up for this, then dropped it on you...