According to David and Ben Crystal in Shakespeare's Words (Penguin, 2002), Gaultree is now Sutton-on-the-Forest, North Yorkshire.

I can't find the reference to Langley in Richard II at 3:4 -- are you sure?

And there are other places you don't mention -- for example, the Bishop of Ely's strawberry garden, mentioned in Richard III 3:4, is at Ely Place, Holborn in central London.

H.