You might find it helpful to go to:
http://www.moneysavingexpert.com/reclaim/bank- charges
which will explain the up-to-date situation regarding people who are claiming back high bank charges. From this it would appear that all claims are currently on hold depending the outcome of a Court case.
In the meantime I can only suggest that you talk to your mortgage provider very quickly about the state of your mortgage , rather than letting the situation go by default. Perhaps they would allow you a payment holiday, paying interest only, or allow you to extend the mortgage term which would bring your mortgage payments down to a more manageable amount evey month. Whatever you do, be pro-active in trying to stay on top of the situation.