"Sparks" wrote :

I think so, but it would be better to connect to the input of the spur (Or
place a junction box on the cable between the spur and the consumer unit,
and connect to that), then you have a socket that wont blow a fuse if
something bigger was plugged in to it at a later date (and take out the
heating system!)

Thanks for that. Good point about taking the heating out. The thing that
worries me about having a socket on the immersion heater/CH radial is the
mixed use aspect. Would someone coming later realise that they need to throw
the CH MCB to isolate that socket? Perhaps clear labelling at both socket
and in the CU might be sufficient?

Steve S