I'm looking after a small property in the country where it gets particularly cold in winter, there's a new outdoor pump installed which run the mains water to the house from an aquifer. I'd like to build a simple and cheap insulation solution to prevent water freezing in the pump.

Current plan is to have an insulated box over the pump, with a reptile heat lamp (or even just a low wattage incandescent) inside which is controlled by a thermostat. Before I make anything I was wondering if anyone here had any particularly effective methods for accomplishing the same task?