Proportionally, not very many at all. Of course there are the odd few who go along just for the ride without any real academic stimulation, but I'd wager that for the vast majority learning is the main criteria for picking a University. Of course they talk about the nights out, socialising etc...
The key difference which many are forgetting is that degree loans are currently interest free i.e. if you owe £21,000 at the end, thats the amount you are expected to pay back. What this report suggests is that interest will be earned depending on how long it takes you to start paying it back...