Hey, I'm currently training at the college, to answer your opening questions, have a look at the article locked on the top of the ATC forum you will find plenty of information there regarding the selection process.
You do not have a licence while you are a trainee at the college; whilst you are at the college you are working towards attaining a student ATCO licence which will enable you to commence further training at a unit. Once you have been through the full training at the unit you will get a fill ATCO licence. Both are issued and regulated by the CAA.
You have a lot of work to be done inside and outside the college in order to pass the exams and absorb the knowledge you need to do the job, so if you go for it be prepared to work hard.
Hope this answers some of your questions, good luck with whatever you choose to do.