Summary:
It is: a single, existing, permanent, manufactured metal object in the U.K., bigger than a phone box and smaller than a shipping container, big enough to get inside (laughter), at least as wide as tall, um er briefly associated with a TV series, and without moving parts.
It is not: a form of transport, or any of the specific things mentioned so far.
This one is ABSTRACT
(No - not as such - more just a general sense that the question could lead in the right sort of direction)
So, it's over to Flerdle
I'm having some network problems here, so sorry for some delay over the next day or two.