Pay off my Help to Buy?

FillBee

I was about to pay off my Help to Buy Equity Mortgage I got 4 years ago (next year, we start paying interest). The reason for doing this was the Help to Buy valuation of my property was I believe 15% under its actual market value (New build so the same house on the Estate has sold for much more so 95% confident). However, with house prices predicted to fall and my mortgages fixed term finishing next year should I put this cash into reducing my mortgage as my calculations are that the Help to Buy interest rates will be less than the mortgage is probably going to be? 
Any support/opinions appreciated.