Should I keep some mortgage to make future borrowing easier?

In our weekly Question Time, you ask Martin questions on anything and everything, and he does his best to answer them. This week: if I have a lot of credit cards, should I cancel any unused ones? Should I keep my mortgage debt or pay it off? Is Martin working out? A double helping of student finance, and more! If you’ve got a question for Martin, email it to MartinLewisPodcast@bbc.co.uk, and it could be in the podcast!