Further thoughts...
I'm not sure how it works in South Africa but ATSA "qualifications" are not worth a lot in the UK. We are trained and attain "Validations" whether it be on simulator disciplines or ATC sectors etc.
If you want to get a tower licence as a controller, you will need to apply to NATS like everyone else. Your ATC experience/background will probably help you towards this and give you a headstart on other ab-initio recruits.
Good Luck