You can make withdrawals from your savings account, for free, at any time after the “initial period” has been completed, as long as you leave enough in the account to keep it active.
If you want to fully close your savings plan early, yes – you will have to pay any account fees which would have been paid anyway if you had kept your savings plan going until the end of the selected duration. This means that closing it near the start of the plan is completely pointless, because even though the account fees are small, if you haven’t yet paid in very much, you’re going to receive somewhere between close-to-nothing and precisely nothing – so if you’re not committed to building up future wealth for Future You, don’t start a savings plan!
It also means that if you want to close and withdraw your savings plan near the end of your selected duration, the remaining account fees are very small and therefore will not have any significant impact on your overall savings value. This is really useful if you are near the end of your selected duration, have a savings value which has already reached your target, and you want to crack on and use the money – you can, and you won’t have to pay big penalties to do it.