Dingdongler

I've been looking at permitted developement rules for side extensions. These say that if you are within 2 metres of the boundary the eaves height must be no more than 3m. Which part of the roof defines eaves height? Is it the highest part of a double pitched roof, or where the roof sits on the wall?

Also under perm' dev' rules it says you cannot build if it involves 'the removal, installation or alteration to a chimney, flue or soil or vent pipe'

By this do they mean an underground soil/waste pipe/drain? I have one there on the side which I might need to move. By flue would that mean where my boiler and kitchen extractor exit, this would also have to be moved.

Thanks