You are correct; Matra was the name of the team in 1969, but it was a joint venture between Matra and Tyrrell, so Tyrrell is sometimes counted as winning 3 Driver's Championships. I have changed the clue to avoid any confusion.
Fun idea and good Qs but I think it needs a bit more time for us less nerdy f1 fans to wrack our brains :) I only got as far as T and that was with skipping the ones I needed more time on.