If nats have determined that enough desirable candidates can be found who are willing to train for the new pay scale then they are absolutely correct in what they are doing.
Whether it is correct to retrospectively apply this new scale to applicants who may have families and mortgages, and consequently, may have to withdraw from training because they can no longer support those families is another matter.
For me the fairest solution would be to apply the new pay scales to all applicants from this point forward.
Out of interest, how do the older students with aviation experience stack up against the college leavers during training?