Last two,17A, i know i should know this one but just cant think of it, surname of Samuel Johnson's friend and biographer -o-w-l-.
23A Frigate bird that might put you in mind of the Royal Navy, m-n/-f/ -a-, I'm thinking man of war, but i don't get the bird bit, thought a man of war was a jellyfish
23 The frigatebirds are a family, Fregatidae, of seabirds. There are five species in the single genus Fregata. They are also sometimes called Man of War birds or Pirate birds.