You need to take a cbt course.you can ride a 50cc with this under your belt upto 2 years but if you want to ride a bigger bike you can go for an A1 or A2 licence.
A1 allows you to ride no bigger than a 125cc with a max power of just under 15bhp.
A2 licence allows you to ride medium sized motorcycles upto 33bhp with a power to weight ratio of 0.21bhp per kg.To get the A2 licence you must sit the test using a bike bigger than 120cc yet under 125cc thats capable of 62.5mph.
Theres also a new accelerated access that folk will need to look into as they might not need to take direct access.. depending on circumstances/age.
Do it now before 2013 as they will only make it harder and harder! I think 24 years of age is going to be the minimum age for riding big bikes in a few years so its not all bad :O)