I don’t know of any dedicated historical events. Certain groups of gamers bring some pretty big games to several shows. James Roach had a great looking Zorndorf game this year.
The Loose Association of Wargamers have a game in North Yorkshire in the first weekend in May. We tend to do an 18th Century Imaginations game every other year. Next year we’re planning something different but we’ve got too many figures painted to leave them idle for too long.