Good advice from all posters. It is unlikely that your lender's SVR is more than 6% now, but who knows what it may be at that time. You shouldn't do anything at this stage, and you may well find that you will be better off when it comes to an end. Be careful about changing to make capital repayments though, because when the fixed rate ends, you may be stuck with that payment arrangement at the new rate, whatever that may be. You may not be able to change back to interest only if you need to.
The main thing is don't panic. When the fixed rate ends you will not need to change lenders, and based on current rates your payments should not increase, and may even go down.