What the training does is, subject to passing a lot of exams, provide you with an Air Traffic Controllers Licence. This is valid throughout the UK (maybe EU now?) but it has to contain ratings for particular types of ATC work. At each unit you maybe posted to, the ratings will have to be validated for the unit. At larger units it may take a year to train before you can obtain validation(s) for the ratings in your licence. There is a great deal of work to be done and it may be several years before you can operate "solo". Good luck.