pay off my mortgage

I currently finish paying my mortgages (2, one taken out to settle with my ex) in April 2028. I want to pay them off before I’m 55 in order to help toward the goal of retiring at that age. I therefore have 14 years to pay them off (as compared to the current 21), but will try to shave a couple of years off that.

To achieve it 12 years I need to ‘overpay’ (ie additional payments) by £295/month. If I can achieve this, I’ll also save a very handy £49,200 in interest. Motivation if I need it…