Cheers downsizer, thanks for the update. Under the LTR which introduced the SAC(T) the original entry points were Mech Mech and Mech Tech. Mech Techs, from what I remembered, were recruited with a guarantee of attending their SAC(Tech) course following their initial first tour. The courses were stripped down versions of the old FT courses and hence were shorter. The Mech Mech I believe could be offered an FT course based on performance and aptitude. LTR also looked at multiskilling from which came the amalgamation of the trades.
After graduating the SAC(T) would then progress through their modern apprenticeship by work placed evidence being assessed by on station verifiers (SNCO level). Pay breaks at certain points were designed to provide some additional motivation. Progression beyond SAC(T) was by competition through the annual promotion board system. At the time I left it had settled down and all seamed to be working well. Interesting to see how it has developed.