No I've not, but then I'm not a diver so am limited to Stoke 1 and 2.
Moving swiftly off topic, around 10 years ago I saw something very definitely alive in the lower end of Raven's Well in Bristol. I got a glimpse as I disturbed it and it shot downstream into the low area at the end. It Iooked like an eel, maybe 12" long, but it was moving quickly and could easily have been a fish.
The mystery is where it could have come from as a direct connection to the River Avon seems unlikely. IIRC I read somewhere (probably MU5) that the water from the conduit was re-routed to supply the GWR engine sheds once it was discovered. As all the railway depot infrastructure has been long demolished and the site prepared for redevelopment, I assume that the water now dissipates into the ground below the site. Raven's Well is well above the highest possible tides on the Avon, so I'd assume the most likely mode of entry would be as an egg on someone's boot?
I've been back 2 or 3 times since over the years and seen no signs of anything living in the stream since.