Definitely picked a tough first listener to attempt. Struggling to work out the ailanthus clue and a few others. Think I have managed to get the top half almost complete so a lot of jigsaw work with bottom half at the moment.
Smithsax - Can see your conundrum - As a 'long in the tooth' Londoner' was always aware of it ( followed by g*p) - But people younger than I seem to think it refers to H-shire not N-shire!
Charlesberg - Not sure if you were asking for hint. But that one is a simple answer but complicated word play - canopy (4) + endless layer (with first letter being the extra letter) + end of ailanthus.
Having thought I was close I have a conundrum in the NW corner with clues leaving me an unknown APNA?? (Using one circled letter and three from across clues) am I on the right track?