Thanks to all who replied - I seem to have stirred up a hornets nest. As it happens my mains incomer is split already and goes to 2 separate meters (1 for house 1 for steading) They both go into the same fuse box but have separate power and neutral busbars so presumably I can just isolate the house side and leave a light switched on in the steading to tell me when the power comes back? Does that satisfy the safety requirements?
Ken