With regards to Cwmystwyth, the crown estates have fenced shafts and levels. The entrance to (Bonsall's) Level Fawr has been grilled, but someone has 'modified' it. I was there recently, I didn't go to other levels (Rosa, Jackilas, Alderson's, Taylor's etc) to see how the access is, but it's not far from me, I can easily go back.
I know someone in Ceredigion County Council who has been involved in the access question, I'll try to contact him.