What is your interest rate, is 1100 repayment a full repayment or a reduced payment, if not the full, what should it be.
What are you paying towards the arrears. You mention 'equal payment to arrears' what does that mean.
Forget about rent a room for now. How much of your income of 2400 do you need to live on. If you pay 1100 plus 100 out of that, it leaves 1200, are you able to live on that? Heat, light, car, food etc. Do you have a credit card. How many years remaining on your mortgage and what age are you.