I would have a word with your mortgage company to see if you can swap.
Sharing from experiences of dealing with debt
The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively.
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It is fairly easy to do, with the agreement of your lender of course, however some mortgage companies will require you to demonstrate that you have an alternative repayment vehicle in place - such as an endowment policy or ISA which could negate the benefit of having the extra money.