Watch os3 series 1 dead battery by afternoon

Hello,

I've updated my Apple Watch Series 1 to use watchOS 3, the process took a fair while, the Watch app on my iPhone 6 said it was downloading "20 minutes remaining" then "2 days remaining", then my watch died around 3pm (watchOS 2.x), I thought because it kept trying to poll it or something it just died.. fine no worries. Plugged it in when I got home, charged and started the update again, tried to add some apps to the watch while it was updating but they failed, os update eventually went through.

Then first day of using watchOS 3 my battery died again, roughly around the same time as when I tried to update it, baring in mind it usually lasts all day with around 40-50% depending on if I went to the gym that morning.

Now this morning, from full 100% charge its down to 90% within the first hour, and now 80% an hour and half later.

I've removed all the apps from the dock, restart etc to see if that helps, no luck.

Anyone getting the same issues?

Cheers,

Sam