Management is concerned that the goldfish in the pond are, as last year,
going to die if the pond is frozen over for anything more than a few
hours, so it looks as though I need a heater, a thermostat to turn the
heater on when the temperature drops to ~0ºC, and an outdoor socket.

Toolstation do a suitable socket
(http://www.toolstation.com/shop/p77440), Seapets sell a heater
(http://www.seapets.co.uk/products/po...ef=googlebase),
but I can't find a thermostat.

Anyone able to suggest a source for the thermostat? Comments on the
socket and heater would also be welcome.