Firstly, John's figure on the left. This, I believe, portrays the Duke of Wellington. I have encountered a few other examples over time. Their owners and I have speculated on the subject’s identity, but this example titled Duke of Wellington in the Potteries Museum settled that debate. You can read about it here.
Let's get back to the Derby modeler Pierre Stephan. In his book Derby Porcelain Figures 1750-1848 (pp 405. 406, 460), Peter Bradshaw notes that the very last soft-paste models were created at Derby between 1792 and 1810 and among them were four figures portraying four renowned admirals: Admiral Hood, Admiral Duncan, Lord Rodney, and John Drinkwater. These four models are stylistically similar to the Derby figure of Admiral Lord Howe, an example of which occurs marked P. Stephan. Pierre Stephan freelanced from about 1773 until 1798, working for Wedgwood and others. Bradshaw concludes that “The evidence suggests that the five portrait Derby figures were all created by Stephan between about 1794 and 1798.”
At this point, it seems reasonable to conclude that both John's Staffordshire pottery figures were also modeled by Pierre Stephan between 1794 and 1798. And in addition to the distinguished admirals he modeled in porcelain, Stephan modeled an earthenware figure of a prince who never became an admiral: Prince William Duke of Clarence.
Disclaimer: My knowledge of American history is scant, and I know even less about flags, so shout if I need to correct anything. Any porcelain collectors who can shed light, please comment.