I did get up there on the 1st, sorry Hammond, didn't get a chance to check out your track.
Everything above the tramway was blocked, most with a small wall in the bottom and collapsed behind, a lot of digging to clear them, I make these 1 to 7C. 8 (on the tramway) and below were all accessible I think, I had intended to start at the top and work down taking a picture of each as I went but the weather intervened and I got a bit lost, most had about a foot of water.
15 seems to have been drained, a good place to stop out of the rain and eat kendal mint cake, I've dug this ditch a bit deeper.
18 (boiler mill level) has a big collapse which restricts the water flowing from the adit, access is OK but bit broken up, I've removed some loose hanging rock, water was about 1 1/2 foot deep however a friend has been in with it to waist height and Merddinemrys about a foot from the top. There is no obvious tide line. With the height of the fall and enough rain it could reach the roof. One more thing to check is the landslip above it.
I'll try and get up there the day before and syphon off some water from 18.
Fron Boeth open cast seems to have been underground then un-topped, the pit further in has a tunnel leading south east but no access without a climb (but does contain the skeleton of a cow or horse). I didn't enter this chamber or tunnel.
There is also a slightly odd trial where the tramway and pack horse track meet. Very boggy and low but it may have been there before the tramway, couldn't tell how deep the water inside was and not willing to get wet finding out.
Steve, I assume your talking about the mill at the bottom of Pant Mawr, Fron Boeth Mill has the big boiler.
Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it.