Cheers for the suggestions guys, just been playing around with it for an hour and it's driving me crazy!
Have tried two radios, 27 and 40 meg, 4 receivers and about 20 different positions for the speedo.
The interference did get better as soon as I unplugged my transponder (this is located next to my receiver and servo), but still has a mind of it's own, esp once I'm 10-15ft away.
The power pot I have at the moment looks the same as the one on the link.
I've checked all of the connections, moved them around whilst it is plugged in and they all seem fine.
There is obviously a lot of electrical interference being kicked about from somewhere, could replacing the power pot sort this or is it likely to have to go back to ae?
Thanks