At Valley in the early 80s, it was rare, but not impossible, to achieve B1 on graduating from the CFS course, thereby skipping B2. Not sure on other aircraft.
That has always been possible on both rotary and fixed wing but you have to pass the QFI/QHI course with an Above Average assessment. I know a few talented gits who left the QHI course as B1s.
Shawbury was the place to do your A2 because the support system from Internal Standards was there to help assess you and improve your flying and knowledge - you still had to do a lot of personal study though. It required you to stay at Shawbury after your QHI course which happened for quite a few unless the front line units wanted people back straight away.
The AAC had no such systems but I don't know what the RN had at Culdrose.