Even with a lasting power of attorney in place you can still operate your account and withdraw money, issue cheques, set up direct debits - everything you do now - as long as you have mental capacity.
"If the donor lacks capacity, they will no longer be able to issue cheques or authorise withdrawals from their account, for example. If they have capacity, but require an attorney to act on their behalf for certain transactions due to physical incapacity, for example, they can continue to make withdrawals and issue cheques independently".