Mark,
As a ship model maker myself, I also found this of interest. It's a pity though they didn't have a photograph, or I couldn't find one.
There was one small slip in the text, well it is a newspaper (!), in that the article said that the ship had been 'built' by Thomas Slade, whereas of course he was the designer. The ship herself was actually constructed by Henry Adams at Buckler's Hard in Hampshire and launched in 1781. Several ships of the period were built here and it is well worth a visit, if you haven't already been there. It's at a lovely spot on the Beaulieu River in the New Forest. I visited it many years ago and remember a beautiful model of the Agamemnon, I believe in the Master Builder's cottage, which I think was contemporary and was possibly the builder's model.
I imagine David Christian's model was scratch built from plans. Googling around finds quite a few such models, some of them magnificent, and there is at least one kit firm that produces a good model of her.
Your post is opportune, as I had been meaning to post something about the Agamemnon seeing as it is just over 200 years since her sinking off the River Plate in June 1809. This from Wiki:
http://en.wikipedia.org/wiki/HMS_Agamemnon_(1781)