Has anyone any advice to give as regards multi fuel/log/gas fires.
Which one would be more suitable for a finca, we have a chimney.

Thank you.

If you have plenty of wood on your land and you have the time to cut it there is no question a Log burner would be best and cheapest. Nothing like a lovely log fire.

Best advice is both. The log burner will nicely heat one room if it is big enough.  What about the other rooms ?
We started with a stove but after a few winters added gas fired central heating. The problem with the stove was no distributed heat and it tended to be almost out in the morning. The luxury of being able to wake up to a warm bedroom and bathroom were worth the expense. I get thro' a bottle of gas in 7 days on average during the winter. We still have the stove lit in the evenings.

We managed with two log burning stoves last winter in our newly built house.  One chimney rises up to the roof through our bedroom and keeps that temperate, we don't like very warm bedrooms anyway.  I think we had a couple of mornings where we had to put on an electric radiator in the bathroom but the main living area stays warm until the stove is re-lit. 

We spent a small fortune on insulating the house which has made a big difference.  We didn't need aircon in the summer either.

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 ;)

Many many thanks for all your advice, it has all been noted.