For reference for anybody reading with an equally tight spot, the clearance around this unit is 2" to each side, and around 5" at the back. Don't be afraid to push the boundaries of the burner output, this performs extremely well and is powerful enough to eliminate the heating system in an old uninsulated large 3 storey stone house. It also has the capability of being hooked up to the radiator system at a later date too which sounds rather good. A smaller burner didn't interest me at all as per the small one in skodamarks post, it's not the same prospect as we actually wish to use this thing as a primary heat source.
A mate has vermiculite boards around his, they are about 0.5 inch thick though so that is going to reduce your existing clearance
