There are some photos on UECT's web site that indicate fenced but not gated stopes. Mention of gates on some adits but not all?
I've just had a look at Foel Ispri on the UCET site - I think the photos are of the levels above the tramway. I've been in some of them but not crossed the planks as I was on my own.
However, there are a number of levels below the tramway - they are close to the stream that flows down past the building at SH 7057 2010. These levels are not shown on current 1:10,000 map. They had newish-looking gates on them when I was there March 2008 - I think they had been gated to protect bats.
Also, from looking at the map there are a shaft (SH 706 198), levels (SH 706 198 and SH 706 197) and a mill site (SH 707 197) lower down the hill - I've not been to those.
Dave