I have read the following (and similar) frequently –
“Is charging your car from a domestic socket safe? While 3-pin plug sockets can charge EVs, they are not designed to support the kinds of loads for the time periods that EVs require. These loads can cause heating that tests the quality of historic domestic wiring, as well as the socket”
Now the above may relate more to full EVs that take many more hours to charge than PHEVs, but I’d still get my wiring checked first. I guess Brydo had his checked when the outdoor socket was installed.