In reply to pec:
Thanks for the replies, a bit of a specialist question but I know there's usually some sparkies on here!
I think it's about 25 years old and the lowest reading is for a single circuit.
It was getting a bit stressful yesterday as it's for a rental house to comply with the brand new regs on letting and the agents didn't tell me until late last week it needed an inspection. I've got tenants due in on Friday and I've got an electrician demanding an unspecified amount of money to trace and fix a 'fault' creating who knows what mess on circuits that aren't actually faulty.
Anyhow, my 'other' electrician delved into the new letting regs and found that a different electrician can sort out any issues without doing a full inspection and I've got 28 days to do it so panic over. So I've handed it over to him.
Thanks again for replying.