Apple Watch can’t pair and can’t update

My Apple Watch needed an update for a while but I didn’t have enough memory free on the watch so I didn’t do it.

I stopped using it for a while.

I got a new iPhone recently and I’ve just tried to pair it with the watch.

However it wont pair with the new phone without doing a software update. The update keeps failing - I know this is due to the memory issue. But I’ve no way to free up memory as the watch isn’t paired…and I can’t pair the watch without the update!

any help?