I need to buy a couple of plug-in heaters - I can swallow the cost of shelling out for them, but which is the cheapest to run? No sense in buying a cheap heater that costs me a fortune in electricity. So, which is cheapest to run, assuming all are 2kw heaters:
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convection?
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fan?
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oil filled?
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water filled?
And what are halogen heaters and are they any good? The reviews I've read indicate they heat whatever's directly in front of them only, and they tip over a lot, thus can be a fire hazard.
The alternative to plug-in heaters is a new boiler and central heating system. Several grand too much for our measley budget at the moment. 
Calor gas/LPG are out for logistical reasons involving animals, small children, storage and clumsy partners. Especially clumsy partners.
Any tips for keeping our breath invisible indoors welcomed!