There is an incredibly detailed list in AP 1358, which is not entirely intuitive.
I agree, particularly as regards the Accumulated Campaign Service Medal. I think it was an odd decision to place this one with the long service medals, but that is the position as it stands.
SWOs aren't the only ones to get confused. When I mounted a soldier's medals for him in my shop, he was back after a couple of weeks demanding that they be re-mounted as his CSM had told him that the QGJM should go after his LS&GC. I gave him a photocopy of the order of wear and sent him off with the unenviable prospect of telling his sergeant major he was wrong.