in the space between the buildings

That's an excellent point Jazzo - I'll buy that. It certainly fits my feel for UK usage that uses 'in' for reflecting a kind of immersion in a closed-in environment – as Bridget notes, saying “in the M4” or “in Route 206” hi W’ONderman! feels completely wrong for that reason.

I also found myself thinking today that it would feel most natural to say “on the Champs Elysees” and inconceivable to say ‘in’ – so I think you have correctly identified that the usage differences stem from a subconsciously different feel for the buildings and spaces and roads which comprise the whole reference.

BTW Bridget, if you think my refs #3&4 are an odd fit in this discussion, try imagining that Pembury Hill is the name of a road… try swopping the name a bit… Also, there is another legitimate UK version I think: “There is gloom on the High Street as retail sales take another dip in favour of the out of town stores…”

Oh, and BTW I also realised today that my aberrant usage of “on the high street” may have also been influenced by the patterns of Welsh I hear around me every day: their form is “ar y Pendre”, literally rendered as “on the Top of Town”. So I won’t blame all my American friends just yet.. ;)