I forgot to say that after yesterday's exchange, I did listen out for the door to close again and said "thank you" through the intercom. Just now the intercom buzzed (it has a horrid, harsh buzz - I'm sure that's part of the reason I answer grumpy-sounding, it's the adrenalin!) and the postman said "If you open the door I'll put a little parcel through." How sweetly tempting is that? So I did, and I said "thank you" again and he said "alright". See, we're building a relationship. Actually it's nice here, I do know my two postmen to nod at in the street, and that's a big deal in London.