Sky News has a reporter and camera crew aboard HMS Trenchant (S 91) for their most recent "Perisher" PCO examination; they've posted two reports to date: here and here. The first report has some footage of U.S. Submariner LCDR Travis Petzoldt (former editor of Undersea Warfare magazine), who is one of the five officers being tested. The 2nd one has film of a fire drill onboard; it looks like the Brits use smoke generators for their drills. (Much more realistic than sticking hairnets over your EABs if you ask me.)
I'm looking forward to the next report; while my first impression on watching was that the reporter sounded exactly like Eric Idle doing a Monty Python documentary, it ended up being pretty good.
Update 0540 02 June: The 3rd and last report is here; plus, I think I've got the link issues worked out for this video and the 2nd one; you'll have to search for "submarines" if you hit the first "here" link in the main post.