I have to say that the new Albarry mono's also sound sublime with Harbeths; more control than with a croft series 7 but with no loos of subtlety. The Croft 7R is half the price though and you could buy three Series 7 standard amps for one pair of Albarry mono's...
Regarding your question, possible airborn interference from a fridge or similar thermostat? if it's gone with the lid on (the way it was designed to be used ), don't worry at all about it.
I remember Neil as a gentle-man, very helpful and dedicated. I'm sure he'd be happy to help should you ever need it... HiFi dave knows him well and could act as an intermediary if necessary I think..
Tear down these walls; Cut the ties that held me
Crying out at the top of my voice; Tell me now if you can hear me