Thanks Jorge, I'll take a look. Incidentally, I got in touch with the author of AC Warmaster who very kindly responded, telling me that he now uses Black Powder. I thought about that option but it seems to require a little more historical knowledge than I have on this topic. I also quite like even points games and enjoy having army lists to work from. Not very historical I know but for me the gaming experience comes first, the history comes in the miniatures and painting rather than any belief that my games will actually simulate historical warfare in any precise way.
I'm unsure now if I will use BP or WMA, both seem to involve quite a bit of work but at least BP is a live ruleset. I've found an article on using BP for ACW which might be helpful. I'l report back!