Books are a one off cost though, not an ongoing expense. They will cost more than £50. If you are prepared to fund the cost of the books he needs, then buy them yourself (most are available on amazon) and have them posted to him. Otherwise, he can make do with the library.
Obviously he will need some form of note-taking equiptment, but pen and paper is fine and this is obviously not very expensive and not a weekly expense.
Travel- is this refering to him coming home from university? If so, is it reasonable to expect him to use something like megabus- which is much cheaper than trains- to compare, I recently travelled from home to London and back for £15, compared to £70 on the trains. Or is he having to travel whilst at uni? This can get expensive, so it would be worth working out exactly what this will cost him a week.
He will need toiletries, and some cleaning stuff, as well as a small amount of food for weekends. He will also need to pay his phone contract if he has one.
Managing this on £50 a week is very very doable. I know people with lower weekly budgets who are also buying all their own food and some bills in shared houses. This will also give him some money towards socialising, which, whilst not esential, is obviously nice to have.
I would not be giving him any more money as he clearly needs to budget. He can take out a non-assessed loan without your consent if he is really that desperate for extra cash. I have a feeling he may be blowing it all because it is "free money".