I've been watching Sid Perou's videos in my lunch breaks, and cracking videos they are.

I've just finished the Otter Hole video from 1982.  You can watch it here - https://www.youtube.com/watch?v=xR1vTkfQEWg

I wondered, was the sink ever connected with Otter Hole?  I can't immediately find any references to say that it was?

Hi Ali Mac,
  I have seen that film too, the sink is at Itton.There is no connection passable to cavers, but the stream has been dye tested and appears in tunnels left at the end of Otter Hole. There is an article in the University of Bristol Speleo Soc "Proceedings" from 2013 vol 26, which you can access online from ubss website literature archive, which includes a map showing all the known feeder sinkholes.

Martyn Farr pushed the upstream sumps but I cannot remember whether it was to a firm conclusion. The main stream sumps still need completing as well I think.