The most bizarre mis-direction of mail that we received was a Christmas card addressed to our house number/name but a different town, with the correct postcode for that town. Somehow the postcode and town had been disregarded and the letter had been wrongly routed to a house/street in a completely different part of the country which happened to match the address on the envelope.
It's the equivalent of a letter for
5 Any Street York YOxx yyybeing delivered to
5 Any Street Bristol BSxx yyyI suppose if it had been posted locally to us, it may have got unofficially "pre-sorted" at some stage so that someone with local knowledge said "I know where there's an Any Street near here", with the town and postcode being ignored.
We have to be very careful when giving our present address because there is a road of the same name as ours in the nearest town, a few miles away, and that town is part of the official Royal Mail address that is given if you do a back-conversion from postcode to address. So we always make sure when filling in the address online that our village name is prominent, manually tweaking the address if necessary after it's been expanded from the postcode. It's the difference between official Royal Mail addresses:
5 Any Street Village Town YOxx xxxand
5 Any Street Town YOyy yyy