As PN said, the early Nav Rad courses at BCBC Lindholme ran for a full year. I believe students had to do much of the NBS/H2S syllabus right down to circuit level. It must have needed good maths and physics and a real dedication to hard work.
So how did the P staff persuade newly qualified Navs to opt for the Nav Rad training when it meant a further year of hard graft. And it had the prospect of life in the V force at the end of it. It must have been a hard sell.