We are spoiled in the UK: typically 235V varing by around +-2%, but some domestic wiring, which does not conform the the regulations, gives large voltage drops at the wall socket.
Also, the mains plugs and sockets vary a lot in quality, not to mention the workmanship of the connections. It is common to find live and neutral swapped and the earth terminal screw not tightened sufficiently. Our wall sockes are rated at 13A but many are only good for around 5A. You often find plugs on electric fires steaming hot and turning brown.
I don't live in Somerset, but I can assure you that's nothing like reality in the UK - it's certainly NOT common for live and neutral to be wrongly connected, or for the earth screw to be lose - and I've been in thousands of homes installing electrical items and never found one like that.
The sockets are perfectly fine for 13A, and a double socket often feeds two 13A loads at the same time - that's why we have ring mains in the UK.
I have seen occasional plugs on 3KW heaters burnt and brown, but that's normally because the plug was fitted poorly (not correctly tightening the screws, making a 'high' resistance connection that gets hot) - and the heat from the plug pins can also damage the socket.