I have held a full driving licence for a number of years, however I have just passed a motorbike test. Does the New Drivers Act apply to me?

The New Drivers Act applies for the first 2 years following the issue of your first full UK driving licence. Subsequently passing further tests and adding additional categories to your licence does not result in the New Drivers Act applying again. Consequently, having passed your motorbike test, does not restart any probationary period.