WatchOS 4 update taking 3 days?

I've just updated my iPhone 6s and am trying to now update my series 2 watch.

First it said it would take 3 hours to download, then changed to 7 hours and now says 3 days!!! I've checked online and it says the download and install should take 1.5 to 2.5 hours to complete.

What should I do?! I've tried restarting my phone but nothing changes.