Planning ahead enables you to get the best outcome. Typically you can look at remortgage options around 6 months prior to your current product ending its initial rate, as any new mortgage offer are typically valid for up to six months.
This means you can secure a new deal and get everything lined up with plenty of time to spare, saving you money and ensuring you don’t pay more than you need to. Also if you secure a new mortgage rate 6 months in advance, but then rates reduce before you switch you still have the option of moving to a lower and cheaper rate.