Believe it or not I've got one fitted to my MK1 Focus TDDI and it is brilliant. A Kenlowe hotstart. It is a 3kw unit and will heat the engine in about 30-40 mins. Not need to keep it on all night, just use a timer plug.

Instant heat from the heater as well as the fuel savings on cold starts. Have been a real bonus this winter. Quite pricy but I'm looking at keeping it a long time and transfering it from car to car. Should have bought one years ago.

Below are some piccies when I fitted it...