Robbo
By the time that you have finished your exhaustive researches into the options available to you in all the branches of the RN, we would probably have already been amalgamated with starfleet command, and you would be entitled to your own cabin and as much time in the holodeck as you can handle.
If, on the other had you where to join as a OM(SEA) in the near future your future would look something like this.
Phase 1 training-Living in a mess deck at Raleigh
Seamanship traning-Ditto, but in a smaller messdeck
Tactical comms/gunnery training-Ditto but at Collingwood
First Sea Draft-living in a mess deck of 24-36 blokes(This may sound shit, but trust me, its a scream). During your FSD you will be landed for what is known as harmony time. If you harmony time requires you to live in barracks, then you may get a single cabin, or you may live 4 to a room in the block. You may even get drfted to a AFCO near your home address. It might be worth your while finding out where your neaest AFCO is. They would be happy to answer as many bone questions as you can find to ask.
Before you ask, an AFCO is the Careers Office.