Try these http://www.workingwoodlands.info/
as a starter. SCC also own a surprising amount of woodlands, so you could try contacting Nick Sellwood at SCC's Meersbrook Park offices on Brook Road. Also try Len Carr at http://www.syforest.co.uk/
- he is the community forester and may have some useful contacts.
I saw another post of yours - there are a number of cruck barns in the local area but how specific they are to Sheffield i do not know!