Yes Phil, not much left of the original structure from 1765 but quite a lot of the interior timbers on the Orlop deck (where Nelson died) apparently date back to the initial build. To be fair, ships of this type were constantly repaired and renewed throughout their lives, it was the normal process. It's the same with the human body, everything has been renewed several time over throughout our lives except that when you get to our age the process doesn't quite seem to work so well....
Take the Medway Queen, new hull, new upperworks and just about only the engine remains from the original. On the other hand, the remains of the Mary Rose are actually original.
Colin