] When I first thought about it I supposed it unlikely that JA had any connection with Nelson but in fact her brothers Francis and Charles must have talked of him. Not sure if they ever served directly under him or Suckling?

I'd think if either of her brothers had an opportunity to converse with Nelson, it would have become part of family lore. However, the Admiral did write in March 1805,

"I hope to see alongside a French 80-gun ship, and he cannot be better placed than in the Canopus, which was once a French Admiral's ship, and struck to me. Captain Austen I knew a little of before, he is an excellent young man."

I'd say knew "of" would indicate that it is likely they did not meet, or if so only very briefly.

Admiral Louis hoisted is flag in the "Canopus" which took part in the chase of Villeneuve's fleet to the West Indies and back. It did not, however, take part in the Battle of Trafalgar.