It rather depends if your looking to maintain a temp all the time, as Oil-filled radiators take longer to heat up a room, so if your looking to maintain a temp oil-filled would probably be cheaper to run, however if your looking to come on an hour before you get up and then a few hours in the evening you would struggle to find one big enough to heat the room fast enough.
With regard to convector compared to fan, the main issue is convectors work by having the majority of heat in the ceiling and cold air at the floor, so you have cold floors effectively, and lose a lot of heat in the ceiling, as such I would suggest out of the two you go with a fan heater which can disperse the heat evenly, and you need the ability to warm a room up within half an hour.
Please let me know if you have any follow on questions.
I work from home so my office is in my bedroom. Rather than having the heating on during the day in the whole flat and having to adjust the radiators in the other rooms for the evening, I thought it would be more cost efficient to have a heater in the room I work in.
I would want to maintain the temperature for the whole day and it would be ok to take a bit longer to heat up. I am really looking for the most cost efficient solution to keep bills down but keep the room warm.
From that, would you say the oil filled or convector is better? Thanks.
From what your suggesting I would probably say an oil-filed radiator is your best option, that said per amount of energy given out electricity is 3 times more expensive than gas, so when you consider you could have three radiators running on gas central heating for the cost of one radiator on electric, you will probably find its cheaper to install TRV (radiator thermostats), and turn them down in all the rooms your not using during the day and turn them back up in the evening.
Appreciate its still vague but it takes alot to make electricity cheaper than gas when it comes to heating, and if the other rooms are colder eg the hall way the heat will escape during the day, so I would argue your best sticking with Gas central heating, which is what I do (as I work from home).