Hm hadn't actually tried that. Doing it now.
I've uninstalled as many third party apps as I can, just in case one of them is responsible. I've also just unsynced all the music I had on the watch (which I rarely used, but it was there) just in case that's causing a problem.
Look it's not the worst drain, but it's definitely noticeable after the update. Like I would get to bed time and still have at least 30/40% left even after using the watch for Strava or Yao Yao during the day. Last night my watch was flat by 8pm.
Next course of action is a complete reset/repair of the watch (which I hate doing, worst part is having to re-add all your debit/credit cards)