One mistake you can make is aggressively overpaying your mortgage when you already know you're planning to refinance and take that money back out. Imagine you have £30,000. You put it into your mortgage. A year later you need £30,000 for a business or another property. Now you're going back to a lender to release equity and potentially paying interest and fees to access capital again. I'm not saying don't overpay your mortgage. I'm saying understand your future liquidity needs before you overpay