It is a 20amp switch, although very old. The wires were secure, although visible heat marks around the live input.
I'll replace the switch and thermostat and will monitor..
Thanks.
My boiler needs replacing, therefore I switched on the immersion to use in the interim, although it didn't cut off once it reached temp and ended up boiling the water in the tank. When I turned the hot tap on, steam came out initially!
The immersion switch was also too hot to touch and had that...