Are you allowed to have a woodburner in a flat? I know they had open fireplaces, but all the flats I've seen have had the fireplaces boarded up.
There was something years ago about setting fire to the other properties if anything happened, but maybe that doesn't apply any more.
The other thing is as already mentioned, the bringing up of the logs, but if you have the storage room......
We have oil central heating, but I only have it on for an hour in the morning, and 2 hours at night, so all through the day, its the woodburner. A lot of the logs we buy are softwood, which doesn't last as long as the hard wood. Last years wood came to £400, the oil for the year was £600 and electric is £46 a month, so you'd have to work out what's cheapest for you.
Saying that, I do like our woodburner, but luckily, the log store isn't far from the patio doors! lol Good luck Surbie!