Once you reach the age of 19, you can apply for your A2 licence where you'll have the opportunity to ride up to a 500cc engine size, with a power output of 35KW (or 46.6bhp).
To qualify for the A2 licence you can either:
Wait until you've held your A1 licence for 2 years and then take the practical test
If you're 19 or older, you have the option to take the Direct Access route which involves completing your CBT and passing your Theory Test & Practical Tests.
Once completed, you can ride any A2 category motorbike or scooter without the L plates, as well as carry a passenger.