
If interest rates go up your payments will go up. As these mortgages tend to be linked to the lender's standard variable rate, if the Bank of England decide to reduce interest rates there is no guarantee the lender will pass any or all of this reduction on to you.
Charges are likely to apply if you want to repay all or part of your mortgage balance during the discounted period, although some lenders are happy for you to make limited lump sum reductions or even transfer the mortgage to a new property if you want to move house.