A year ago my father in-law had built up some debts, unable to make the repayments he asked if we would take out a mortgage on the house. He was planning on moving to America or traveling and using the house as a temporary base between trips. 20% equity of the house was signed over to my husband and I, at the same time all three of us (father in-law included) took out a mortgage on 20% of the property. 85% of the Mortgage money was given to my father in-law to facilitate his move/traveling and my husband and I kept the remaining 15%. At the time we had a verbal agreement that we would pay off the mortgage in exchange for full use of the house under the understanding that this would not by my father in-laws permenant abode.We also agreed that if the house needed to be sold that the mortgage would be paid off by all and the remaining funds split 80:20. We did not draw up a formal agreement as my father in-law insisted that there was no need. We have now been paying off the mortgage for a year during which time my father in law has been living here. We cannot continue to live with him as he is taking locks of guest bedroom doors and has been casting paranoid accusations of theft at us. we have even had to get the mental health team involved as he has disowned his daugher and believes he is Jehova and is on a mission to save the world. He was sectioned a few weeks ago but did not admit any of this to the Dr's so there is nothing they can do to help. He has finaly agreed to sell the house but only on the condition that we pay off the mortgage from our 20% of the house, which with the housing market crash would leve us in debt. Is there any way in which we could force sale of the house and hold him to his side of the mortgage agreement and the verbal agreement we made?

Thank you for you help.