I think the path you are talking about is Marriott's Way - running from Norwich to Reepham on the course of an old railway. It's part of National Cycle Route 1 (Harwich to Hull).
http://www.sustrans.org.uk/default.asp?sID=1104929243171
Contact Planning and Transportation at Norfolk County Council (pt@norfolk.gov.uk) for a route map / information leaflet.