There are two main points to be made for this point of view.
The first can be made on the basis of social equity and fairness. From this point of view, university should be free to all so that all people can have an equal chance to attend and to get ahead in life. It is absolutely unfair that anyone should be prevented from going to university because they lack the funds to do so.
The second is a more pragmatic argument. It says that Britain needs more university graduates in a globalized economy. Britain will not be able to compete well with other countries unless it has more university graduates who can fill jobs that demand a good education. Therefore, Britain should make universities free to all so as to improve its competitiveness in the world economy.