In reply to pork pie girl:
I got an idea for mine, its going to be built out of a wall with a fireplace, so i'm thinking central main board 30-32 degrees, and then making the recesses either side 45 degrees.
Then make one side a small slab and the other side something horrid like 35 degrees for a metre then 50 degrees up to where it meets the main board and the roof. Will leave the the first metre or so from the base of that 45 just following the wall, so i get a kind of little sit start 'cave' on that side.
So some fiddly angle cutting at least!