I know a single line exixts passing from the city thru Wadsley Bridge and Oughtibridge but how far does it actually go? All the way to Manchester?

If not does the old track bed still exist to Manchester so that if ever it was to reopen it would just be a case of laying track/signals etc or have housing etc been built over parts of the route make the possibility of it re opening virtually impossible?

Use the 'search site' button. There's quite a bit about it on here already, and some forumers seem to be members of groups with a particular interest in it.

but this may help (http://www.central-railway.co.uk/maps/map12.htm)

It terminates at the steelworks in Stocksbridge. There used to be a rail link all the way to Manchester but it was shut down in the early 80's. It's now a trail/cycle path which you can follow from Penistone to Hadfield on the Manchester side. Well worth walking if you're into that kind of thing.