Now to answer the question. Things may have changed a little bit but this should be pretty accurate. You can ride a 50cc scooter on a car license, but you must also pass a CBT test before you can ride on the road. You can then ride a 125cc motorcycle of a maximum of 2 years with a provisional license (CBT) you then need to take a full test or redo a CBT. Depending on how old you are there are 3 options, if your under 21 the first is take the test on a 125cc and that then gives you a A1 License , which allows you to ride a light motorcycle which will be upto 125cc and a power output of 16.4Bhp. Secondly again at 17 you can get an A license which allows you to ride a motorcycle of under 33bhp, after 2 years this restriction is lifted and you can ride any motorcycle. The final option is called Direct Access which is avaliable to 21 year olds and over, this allows you to ride any motorcycle.