My thoughts depend on how modern you want to go, I think its a great idea and a fairly novel take on post apoc gaming. For example looking at various figure ranges available you could think about a late 1980's early 1990's start, which would enable you to use, for example, the Falklands war Brits from Gripping Beast's MoFo range, many of the civilian types from the various Very British Civil War ranges would be nice and useful, plus many of the Doctor Who figures perhaps,and as has been already said, the "Geezers Shut It" figures, also, there are plenty of diecast vehicles, both civilian and military from those periods around. For inspiration, there was quite a body of British "Post Apoc/Sci Fi" literature from back then, writers such as Edmund Cooper, Micheal Moorcock and the Jerry Cornelius saga to name but two.