Comment
But there is more: your bike is also in the post war KeyCards, meaning that after the war it also served in the BAOR (British Army on the Rhine). From the KeyCards we know that the post war registration number was 92YC27, and that the bike was disposed off on July 31st 1957. Which fits the fact that your bike was first registered in 1958. Lex can do you a high-res scan of this KeyCard for a modest sum. I've also added two post war pictures with YC registered BSAs.
email (option): wd.register@gmail.com