As in many cases, the extent to which one organisation is considered part of another may depend on context, but in BR 3, for example, (http://www.royalnavy.mod.uk/news-and-events/reference-library/~/media/files/navy-pdfs/news-and-events/naval%20publications/br%203/br3book/ch01.pdf) the wording used is "Throughout this publication, “Naval” refers to the Naval Service, comprising the Royal Navy (including QARNNS and Chaplains), Royal Marines, Maritime Reserves and the Naval Careers Service." -