I'm no expert but I always understood that the owner of a copyright has to prove that the alleged breaker of that copyright has caused them loss of money. If no-one is charged for watching the vid then I should imagine that it'd be difficult to prosecute you, as by definition there would be no loss to recover. Don't rely on this though as I'm not a legal type.
However . . . why do TV types always have to make caving look far, far more difficult than it really is? For example, take the Swildon's Sump 1 free dive. Next time you watch the film, set a stop watch going and time how long it "took" for Kate Humble to dive through. Then bear in mind that the sump is only 2 or 3 feet long.
However, on the whole, much of the film was pretty good although perhaps a long way from being "ultimate" caving. And I think that the two presenters did pretty well, even if they were carefully supervised. I know quite a few experienced cavers who hesitate to go on a Titan trip and I well remember free diving Swildons 1 myself as a teenager, as my first ever sump - it took a lot of commitment. So I think they did extremely well. The very last scene was a disappointment though (in terms of caving PR).