Our House is late 40s Semi (ex local authority) and probably rewired 60s / 70s. We have a lot of circuits compared with most, and most sockets only have one T&E. Most crcuits cover a some or more sockets upstairs and downstairs. I decided as I wasn't sure of the topology of most of the circuits to have them fitted with 20A MCBs rather than 30A when we had a new CU. We've only tripped once tripped a circuit by pulling too much consecutively, and we just moved the cement mixer onto a different circuit for the day. I did do a continuity test in the CU on one of the suspect circuits the other day and it does appear to be some some sort of ring (at least in parts (but I realise this is simple test is no guarantee of anything). I found out the hard (amd painful) way that the circuit previously labelled upstairs Power wasn't! I now also test to make sure things are dead before I stick my screwdriver in!