Wow, it's great to see a Mumsnetter from Canada! Happy Canada Day for last Monday!
You're right, a Netflix Cananda customer can access Netflix US content when in the US, and Netfix UK content when in the UK.
For Madamecastaflore, I'd assumed she would be living in the UK and planning a holiday in Europe. Under this scenario, her Netflix subscription would only work in other European countries with a Netflix service - currently Ireland, Denmark, Norway, Sweden and Finland. If a UK Netflix subscriber tried to access the service in these countries, they would not get UK Netflix content, instead they would get local content for the Netflix country they were in. If you tried to access Netflix in any other European country, the service won't work.
Maybe stock up on some good books and magazines for the holiday?
TarriffHound - That's not correct. I'm subscribed to Netfix Canada but on trips to the USA and the UK I just log in as normal and get offered either the US Netflix lineup, or the UK one, as appropriate... The workarounds you're referring to are actually for people (like me) who get sick to death of their domestic Netflix offerings being so limited and crap compared to the USA and UK, so choose to fool Netflix into thinking that they're physically located in a different country and therefore get a far wider range of movies and TV shows to choose from!
Hi, it will certainly work if you're holidaying in the UK, but not if you're going outside of the UK. Netflix will check to see where your internet connection is originating from and block if out of the UK. There are some technical workarounds you can do to trick Netflix into thinking your internet connection is coming from the UK, but they're pretty techie.