Previously I have found a possible ancester using the link to The National Archives: Trafalgar Ancestors. I thought I'd already posted about this, but can't find the entry.
Thomas Hendra aged 21 born in Gwiner. Ship: HMS Achille. Rank/Rating: Landsman
With my current family tree, I can with some confidence go back to a Hendra in Gwinear, specifically James Hendra (born around 1832) married to Jane Carter.
From here on back, I'm on shakier ground, but believe I can say that James was the son of John and Elizabeth Hendra. According to the 1841 census John was 45, so born around 1796. There's a baptism record for a John Hendra 22nd October 1796, son of Thomas and Jane.
Is this the Thomas Hendra of the Achille?
Okay, it's starting to look more dubious now. The only valid baptism record for a Thomas Hendra I can find is 2nd July 1780, which would make him only 16 when John was born, and that's a young age to be a father in that era (most of my other relatives start producing about 20 or 21.) It would also make him 25 at Trafalgar which doesn't tie in with the official age, although the advice on searching suggests the ages on the ships' muster rolls are not that accurate.
So, perhaps not a direct descendant, but probably related to my branch of the family - in the 1841 census there were only 4 or 5 families of that name in the parish. He 'ran' from the Navy 1st March 1814, and I haven't managed to find any reference to him after that, but I hope you made it home, Tom.