The best advice I recieved some years ago regarding log burners was that if you use one infrequently then choose a steel one as it can handle multiple cold starts and heats up quickly. A cast iron one needs to be heated gently and is better suited to regular use as it retains its heat for much longer.
In both cases expose the chimney flue to the room(s) as this is where the bulk of the heat goes!
You can get a thermal fan that sits on top of a wood burner that spins faster as it gets hotter therefore pushing warm air into the room...... and finally....I was told to throw a 2kg bag of salt onto a roaring fire once a year as it clears the flue of tar and resin which can be considerable if you burn pine logs.
Hope this helps ;)