Okay I think I may have found my answer (though please correct me if I'm wrong as I really would like to know for sure).
I read online that the steps in the movie where Nancy tries to see off Oliver and is eventually killed by Bill Sykes ARE the steps used in the movie but pretty much all of it was later removed and deported somewhere
(Arizona I think it said
) but "they" (whoever they may be) kept strictly the steps.
God Immigration were harsh in those days !
The old London Bridge was sold and exported to the USA but the steps remained.