Dude your answer is Halogen (if you don't manage to fix your radiator that is), search for '800 WATT PORTABLE ELECTRIC HALOGEN QUARTZ HEATER' on the bay, they are as cheap as chips, well almost, they cost about £12 inc delv, they are small and not very imposing, they are very simple but quite effective at putting out heat, I used to use 2kw fan heaters until I discovered these baby's, 800watts may still sound like allot but for the amount of heat they give off they are very cost effective, they manage to heat my large double room up to around 24 degrees Celsius and then I switch it to one bar @ 400watts and it keeps the room toasty for as long as I like.
There in no real cheap solutions when it comes to heating but halogen is a good compromise compared to fan heaters, old fashioned bar fire heaters and convector heaters etc.
Also dude, don't get the large Halogen heaters that go up to 1200watts, they are like having a floodlight in your room, I brought one home one day and just lol'd when I turned it on, these mini ones just emit a warm orange glow that isn't over powering, I'd say just a bit brighter than the old bar fire heaters which isn't too bad tbh.
Cost of running, well I run mine for about 7 hours a day (or night rather) the first hour or two I run the heater in dual bar mode (800watts) and the remaining hours in single bar mode (400watts), I have estimated that it is coasting me around £3.50/£4 a week which isn't bad really.