I have no idea what the average is but the poorest students on a 3 year degree studying in London will be £59,106 in debt by the time they graduate, and that figure will only rise once tuition fees start to rise with inflation. People doing longer degrees (language students, integrated master's students etc) will be nearly £80,000 in debt. it seems absurd but studying in the United States is cheaper than the UK these days.
I don't think people will be put off because realistically, what other alternative is there for 18 year olds? If it's a choice between going into debt in order to have the career you want, or not going to university at all and being stuck in some dead-end job then there's no choice at all. But the number of mature, part-time and second-degree students looking to retrain has already fallen sharply and doubtless will continue to fall as fees increase.