U267,
I joined with a ppl/ir/night rating and some cpl training: about 200 hrs fixed wing.
I still had to go through elementary flying training as an ab-initio and I thought "I've got this sewn up, harriers here we come!"… how wrong I was.
I quickly realised I had learned some pretty bad habits, my visual scan was appalling, low level nav was new and hard, military circuits were different to GA, etc.
But saying that, I did get streamed rotary, so the hard work and prior experience must have helped.