Yeah, I saw the reference to John Braithwaite, but the context suggests more that he made figures of Plantagenet knights, that is, knights serving the Plantagenets, rather than that he produced figures under the trademark, "Plantagenet." I think Braithwaite actually produced his knights under his own name.
I'm still going through my back issues of "Toy Soldier & Model Figure" and "Toy Soldier Collector", because I'm certain I have seen Plantagenet mentioned in an article. To give you an idea of the extent of the task, TS&MF is up to issue 222, I think it is. It was a monthly publication until last year, when it went to bi-monthly, and I have every issue, except maybe Issue 2. TSC is quarterly, and it's up to issue 72, though I let my subscription lapse last year, after issue 67 (I forgot about renewing). And this is all hard copy, so, it takes a while to get through it.
But in the meantime, you might want to email Carl Hoegermeyer, whose site Quartermaster Collectibles is, and ask if he knows more about Plantagenet. Carl's a member here, too, but I don't know how often he's online and in the forum. Another contact would be the author of the book on Braithwaite's knights, Philip J. Bennett, through his website, Lord Tankerville's Knights. I expect he'd be able to tell us whether Braithwaite also made figures of other periods than the medieval period.
Prost!
Brad