Native timber species (that just might be offered to you) as fuel (all 5% moisture):

 - Beech 17Mj/kg
 - Oak 16MJ/kg
 - Pine 17MJ/kg

(BTU/cord would be little understood in these islands)

Remember that pine is substantially less dense than the hardwoods

A source for the info: [UN FOOD AND AGRICULTURE ORG WOOD FUELS
HANDBOOK][1]

Most important: CLEAN YOUR CHIMNEY!

As pointed out in other posts, soot buildup is a serious fire hazard.

btw, "flue" is the same as "chimney". I suspect that when you state that your "flue doesn't go all the way to the top...", you actually mean that the stove pipe (the pipe that connects your stove to the flue) feeds into a chimney.

What you want to achieve is a sealed system with all air entering through the air intake of the stove, and existing at the top of the chimney. The allows all the air entering the system to be directly available to the burning timber. Ensure that the seal around the stovepipe is good and that the flue has only one outlet (at the roof level). You can seal any dodgy joints with fire cement, available in cans. This should improve the "draw" in the flue.
Ensure that all door seals are good. Install new sealing rope if necessary.

  [1]: http://www.fao.org/3/a-i4441e.pdf