That isn’t Hook it’s Bernard, he only makes that sound once, during the second chorus, and someone has altered the original audio, putting it in a bunch of times.

From the YouTube description:

Reading Festival, Sunday 1993-08-29. Amateur footage from the audience, thanks to odonnellpaul & the person who filmed this. "Getting professional..." - probably the first NO gig that had overdubs for the FM broadcast? (not that it was necessary - it was a great performance anyway) Spot the bits where the music doesn't match the footage!

Barney always whooped on stage, Hook never did.

My 2p worth (I'm English, so no 'cents' for me )

I think it is Hooky, and I think it's him taking the piss out of Bernard.

The two clips you posted above don't feature this, but on the original video, Bernard whoops a split second before he comes in with the chorus. I guess the BBC edited that whoop out, but it's present on the two different video recordings that are in existence.
On the first of these videos (filmed stage left, house right), you can see Bernard punch the air as he whoops. The second film (stage right, house left), Bernard is off camera, but you can still hear him whoop before the chorus.
If you look at the two clips above, you'll see Bernard quickly punch the air before the chorus and open his mouth However, the actual whoop is missing from the audio.

I think this whoop is partly what makes Hook speed to the mike. Partly to sing backing vocals and partly to take the piss out of Bernard's whoop.

Unfortunately, as both cameras are off Hook at the time, we can't say for certain. But there's 1 x 'Bernard whoop' and 1 x 'mystery whoop' present on both tapes.

The audience audio tapes I have (again, two different ones, I think) also have a 'Bernard whoop'. No idea why the Beeb would edit that out, but leave the daft 'mystery' one in.

Just my opinion folks.

Never mind the whoops, that is gold standard bass thrusting and flowing locks that would put Robbie Savage to shame. Sometimes I miss those times.