Yeah I jumped ship to piped too because of this. I also discovered it allows me to circumvent region locks without even firing up my VPN which is a nice bonus
Idk I just went to a channel that I know for a fact only allows you to purchase the videos if you're watching from France, but I was able to watch all the videos for free because they are not restricted outside of France. I think it's supposed to work automatically if your piped instance has access to instances that are hosted in countries where the videos are unrestricted
So in your case it should work if you go through an instance that is hosted in the UK