At the moment I believe Global can only do “Tower training”. In theory I suppose you could do a basic course there then go to CTC for an Area course. I would think this is unlikely because the course progression is Basic-Aerodrome-Approach Radar and it is easier for everyone involved to keep the same people on the course progression.
Also if you have been accepted as a NATS TATC the “option” to choose which course you go on will not be down to you!
Rgds
AyrTC