Have a look here, Kid...............
http://www.communitie...ilding/pdf/143945.pdf
The regulations aren't too onerous at all. Mostly small measurements (300mm, 600mm) from most important features (openings, canopies etc).
Most important for you I guess, is that the outlet must be a minimum of 1200mm (4') from a door into the building.
As far as I know, you don't need a through draft as long as the terminal is outdoors to receive its combustion air.
When you get your quotes, the Heating Engineer will go through it all with you. There's usually a way somewhere :o)



