We're one of the fortunate families who happen to be on a base rate tracker so our mortgage payments have dropped a lot in recent months. This has been great while I've been on mat leave and money tight, but I'm back to work in 3 weeks so we might be able to overpay a bit on our mortgage. How can I work out how overpayments will affect the term of our mortgage (without having to have a ridiculous discussion with some bank employee in a call centre who doesn't know what i'm talking about)?