I was told about some local Heritage Open Days which give access to buildings etc. that are normally closed or have other events. I think these may be of interest but check the Shefield list for others:

Rivelin Valley (Sun 14th Sept 1030-1430)
Underbank Chapel (Sat 13th Sept 1000-1600 and Sun 14th Sept 1400-1600)
Wardsend Cemetery (Sat 13th Sept Tour 1030-1200 & 1400-1530

For a full list of Sheffield events click here