For the personal statement, would it help him to have the viewpoint of a university teacher?
There are a few cases- e.g. medicine- where targeted work experience/volunteering experience actually matters, but if he was going for something like that his school should already have told him.
Other than that, most of us don't give a monkey's what he does in his spare time. There is no evidence that trekking through the Himalayas or winning the junior swimming championships is going to make you even a tiny smidgeon better at studying English literature or advanced mathematics.
All we want to know is that he is going to give his all in his specific subject. A lot of English university teaching depends on the engagement of the individual student: if the students of the seminar group are dull and can't-be-bovvered, the seminar discussion simply doesn't happen.
So we want to know that he is actually interested in it: interested not just to the point where he does what he needs to pass his exams because he is a good boy, but actually interested. That he is someone who has chosen his subject carefully because this is what he really wants to do, someone who is going to go the extra mile, someone who is already reading a bit more than he has to or doing subject-related stuff because he just enjoys it. He doesn't have to gush, but something specific that he enjoys doing that is relevant to the subject would be good. Those videos for instance- could they be relevant in any way?
This is three years of his life where he is going to need to muster more enthusiasm than has ever been required of him before: enthusiasm that will carry him through the early Monday morning lecture and the late afternoon Friday seminar and hours and hours in the library. What is there about the thought of his chosen subject that makes him feel enthusiastic? Let him think about that, put it down, and try to come up with an example or two that prove his enthusiasm.