Forester: "One sergeant, one corporal, twelve privates and a drummer were all the marines allotted to a sloop of war..." So pretty close! Elsewhere in the novel there's a "Captain Jones," but he might well be on loan from another ship; most of the marines in that action against the semaphore station were from other ships.

And at the risk of making you pull out your reference works again, what should it have been on the Atropos? Sixth-rate, 22 guns. ETA: Sorry, I see you have the table up now!

And yes, I eventually did decide that the wardrooms on the Hotspur and Atropos were imaginary, but it's nice to have the confirmation. :-)