Awkward flue installation

[DodgyJammer]

I believe the flue for a solid fuel burner needs to extend a certain distance above the roof ridge (in case of a flue fire).

Many gas stoves can be installed with balanced flues like normal gas fires or boilers. Quite a few gas stoves are on the market (e.g. have a look at the Stovax Gazco range) but bear in mind that generally they're not as powerful and they're more costly to run.

 

[Norcon]

Your flue will probably cost more than the stove.
I'd expect between £700 and £1000. The hole through the wall is the most difficult job. After that its a doddle to fit. Just snaps together like lego.
Ensuring the arrows run in the right direction.
The hole will run at a 45 degree downward angle.