You'll find that, under the Lardy Blokes on the Highway Act (1993), such things are not permitted. Quite rightly, in my opinion.
I know they should be restricted to 28mph but I feel safer knowing that my Son can use the power available to keep up with modern traffic and keep him out of trouble from the muppet brigade. He knows that if he see's th BIB he needs to keep to 30mph.
Rick if you are after a c90 you will have to spend mega buck's as they are going for stupid money! I did my CBT and i can highly recommend it i am looking at doing it again and going for a full licence as i did have a 125 it was a chinese copy of the cg 125 engine and they are great for a learner to get to grips on basic bike maintenance here is a pic of mine!