Thanks for the link 5milesbaby.
I'm still not clear on one thing, if you start off as an ATSA for a non-NATs airport is it possible to do the sudy to become an ATCO without applying to NATs in the way people wishing to work for them do (i.e selection process etc).
If so how is the study completed (i.e self study (distance learning-like some pilots licences)?
Thanks