The waistcoat was an approved option with No 1 at one time, though I never saw one.
I went to the OCTU in June 1972 and was issued with collar attached cotton shirts of the end on end kind. They were nearly identical in colour to the ones worn by officers, but the more expensive officers' shirts had curious curved corners - or lack of corners - to their cuffs. I continued wearing mine until well into the 1970s, possibly early 1980s, gradually replacing them with wedgewood blue polycotton from the clothing store.
Great coats were on the way out - courses earlier in 1972 had been given deficiency chits - we didn't even get that.
When I was doing my basic nav training in 1973, one of my course mates appeared in a pullover - the first one any of us had seen. The V neck was definitely in service by 1987 because I remember OC 30 wearing one when he was PMC and I was Mess Treasurer.