I've been busy all day, just seen all these messages.
I brought an oil filled rad earlier.... Seems to be doing the trick. I thought the oil ones were better as they heat the oil up and turn off. Oil stays hot and keeps giving off heat?
??
As others have said for most electric heaters whether fan, convector, radiant or oil based. The all have equal efficiency. 1Kw of electric gives 1Kw of heating. All that changes is the way they delivery that heat to the room.
The little cheap fan heaters may be marginally less efficient as some of the energy gets converted to kinetic energy by the fan motor. But on the upside they do distribute the heat around the room.
The halogen ones deliver the heat faster further away by radiation. Oil filled heaters I think are the safest for confined areas as they are less likely to get covered and cause overheating/fires.
For a house, I would have bought 2 x 2Kw fan heaters and set them on the 1Kw setting and have them at opposite sides of the house.
If you are going to be there are while and have access to red diesel, maybe a chinese heater in a custom made metal box outside with the heat/inlet being fed into the house. However, you would need to make two holes so allow the heat into the house and the fresh air from inside the house into the inlet.
Just my two pennies.