You can withdraw your money from goals or upcoming scheduled commitments at any time. Any withdrawals made before 1pm on a working day will reach your current account on the same day, otherwise it will be the next working day.
To withdraw from your goals, you simply log into your account, click into a goal and hit the withdraw button.
To withdraw from upcoming scheduled commitments, click the "move them to goals" link at the top of the payments section (as shown below), and you can choose to move any of your upcoming commitments to goals. Once money has been moved to your goals, you can either keep the money safe there - or choose to withdraw it into your current account.