Damn! I had a wood-burning stove installed today, and Clare is too far away.
The answer is that it varies greatly. You might pay between €50 and €250 to have a mature tree felled. Then there is the matter of what happens the timber. It can cost more to have a tree cut up than to fell it, but you can get shedloads of fuel from each tree. If you are not set up to burn timber, you might get somebody to do the work in exchange for the timber.
Be sure that you get somebody who has good professional knowledge, proper equipment, and suitable insurance for him- or herself and for public liability.