Just to add some current information to the "I think" type comments here.
Today, nobody can join as an Ab-Initio SAC(T) other than Armourers. All other TG1 (and this now encompasses all of what was 2&3) join as AMMs. These are Aircraft Maintenance Mechanics, or FLMs of old. Leave Cosford as LACs and are advanced to SAC upon completion of TATs. After 18 months they go back to Cosford to be trained as A Tech M or A Tech Av. Almost like....a fitters course. They leave Cosford as SAC(T)s. We have gone full circle.
Armourers do not go back for further training as they do not have to pass through the AMM hoop and leave as LAC then advancing to SAC, and on Completion of their NVQ are advanced to SAC(T).