Hey, thanks for your advice and prompt response! I have since done a little more investigation and found that the noise stops when I touch the transmitter. I makes no difference wether the guitar is plugged in, or even if there'a lead plugged into the transmitter. Oh and I tried the foil trick but that makes no difference either.
I'm thinking that the transmitter is faulty, it seems like it's using me as some sort of grounding??