"So what stopped the SAR from self deploying?"
In the 60s it was accepted that we could do so and even up to the mid 70s (in Cyprus), however, the heavy hand of the bean counters entered the arena and call-outs for hospital transfers etc. would be billed against the hospitals involved and so it went on. I have been a long time away but I understand that, nowadays, most anything will require 'central' authorisation. 'Crab' will, no doubt, have the correct detail.