Matt i posted my last post just before i turned in last night and one thing kept going throng my mind and that is what you said, ie This suggests its either the mains itself, or the PSU (Diamond switching). When you turn off your mains supply then surly you use battery power to supply your rig? SMPS`s do sometimes cause RFI but if the mains is totally off how can they. Can you explain why you mentioned this. If the RFI is coming up the mains supply then taking out the antenna then it will still be there, if when the antenna is back in nad the RFI returns then it is being picked up by the antenna. You mentioned early this year that you were having your mains supply checked out by a family member, is he a qualified electrician, NICEIC Approved or someone who is doing you a favour. He should be able to check to see if there is something still connected to your mains supply when everything else seems to be disconnected. I will say again a ring main with nothing connected to it cannot to cause RFI, other than if any new electronic meter has been supplied in recent times, which is a very long shot.