Sorry to dig up this old thread, but I have now the same issue, between FR, UK and DE.

I reached out to netflix and here's the info:
1. There is something called the "EU portability" allowing people travelling within the EU to show their content from the country of residence for a little while (didn't precise for how long)
2. With Brexit, the UK is out of this
3. Anything downloaded should be available even when in another country
4. Watchlists are kept when travelling even if the content is unavailable (i.e.you'd be able to pick up on the show whenever you return to the country)

Sadly I won't be subscribing as I want to keep watching my UK shows while in France, and apart from using a VPN (which adds up to the cost and apparently is also blocked by Netflix), there's no solution for me.