It would really depend on who was going guarantor and their financial situation. If it is your father it will depend on his age and earnings, he would really need to be in a strong finacial situation and be able to service a mortgage for the next 25-30 years. Only the bank can give you good advice on this. It might be better to keep the current terms of the mortgage but ask the bank to go interest only for a few years, it would probably cut 300e per month off your mortgage.
If you are not getting any help/information from the council, you should approach your local councillor (they work for you, dont be scared of making them earn their votes, it doesn't mater if you didn't vote for them or even know who they are) and ask them to set up a meeting with you and the relevant persons or even tell them your story and ask them to find out the information for you.
Finally you could contact MABS, they are there to help in situations like this, they can offer great advice and even contact banks on your behalf.