From what little I can recall, theres a general consensus among historians that the modern image of robin hood probably comes from an amalgamation of various historical figures
Also I think nottingham isnt the only place to claim itself as Robins playground, I think some places further north also claim robin hood originated there... If the theory is right about the amalgamation of robins is right then he was probably from a bit of everywhere!! just like me! mwahaha!
On the mythical side of things, I like the idea of Robin Hood as a kind of Herne The Hunter incarnate, which I think is quite popular ( No not just coz of that dodgy 90's ITV series.....)
Will be interesting to see what you you can dig up!