The breakage fee is usually calculated by 6 months interest - I wanted to break out of our Ulster Bank Mortgage and the fee was 8k. I thought they might add this on to the mortgage, but they wanted the payment upfront. Also, unless you are on a variable rate, I doubt you can take a mortgage break. The best thing is to ring them up and tell them your situation. I have found that banks are being somewhat reasonable at the moment, and want to work things out so SOMETHING is coming in to them. They might let you go interest only for a fixed period, but if your LTV is quite high, that may not be much of a reduction. Just ring them, every bank is different so speculation is kind of pointless.