Good point. OK, so I'll split it upon entry in to a set of power
sockets for the fridges and a set for woodworking/tumble dryer
protected by an RCD.

The problem is that the earthing might not be good enough to do this. You'll
probably have to either use an RCD to cover everything (a 100mA Type S would
do, with a 30mA instant on the "RCD" rings which will discriminate), or
upgrade the earthing arrangements. In particular, if you have any plumbing,
or structural metalwork (i.e. the roof) in the building, you should really
main bond it back to the house CU with really substantial cable. This cable
has to have no breaks or junction boxes on the way.

Christian.