I always write my address in the shortest possible (two-line) form: number and street, London +postcode. This is out of consideration for my correspondents who may want to reply to me. I find it very irritating when someone who writes to me (often a commercial firm) spreads their address over several lines, and I feel obliged laboriously to transcribe all of it on to a reply envelope (because I'm never sure how much of it it would be safe to omit.)
e.g.
Justin Elliott
Chairman and Chief Executive
Borchester Land
4th Floor
Lawson-Hope House
29A Lawson-Hope Road
Edgeley
Borchester
BorsetshIre
BO0 0OH