Based on conversations between Shovel6, ICLOCK and myself, we are each aware of different shafts and underground features. There will undoubtedly be more, but as Shovel6 says, this all reinforces the requirement for any 'breaking' and construction work to be done on the site with care.
When the foundry was being demolished in 1986, one of the shafts to the canal was rediscovered when an excavator partially fell through the cap of the shaft!