Ria, we have quite a few of these and used them before we had the boiler in. When the boiler failed we had a 2.5kw one in our bedroom and a 2kw one in our spare room for guests. They were set to the right setting to keep the room at a good temperature and run for 3 months 24x7.
I've found them very reliable and tend to be less temperamental than the element type one's. They do tend to take more time to get up to heat, but they also hold their heat better when they are up to heat and, as I say, I've had several element type one's fail and none of the oil filled one's have ever failed.
If you want to fine tune using it, you could look at something like
this.
I was using one of them on my 2KW oil heater in the attic this Christmas. I also have one on my desktop PC...