You might try looking at dolls houses. Expensive but worth a look.
Worth a look at Sylvanian families (e-bay & charity shops) as some of their
buildings might do.
Britain's western buildings sometimes come up on e-bay.
Worth also putting out a request on sites like 'Free-cycle' & 'Gumtree' who knows
what people have got & are willing to part with.
Another idea, if you want a railway, is buy a few bits of 'O' gauge track. "You
just missed the train"