netflix is part of go binge package so anything watched with that would not come off the 19Gb data you are allowed each month in the EU.
No, Go Binge data comes out of the 19 Gbyte or less allowance when roaming. and counts towards surcharging or cutting you off if you break the (obscure and difficult to find) Ts and Cs. So it's not real when roaming despite what they say. It only works in the UK.
It's only a bonus for people on an "advanced" plan contract with a limited data allowance of at least 12 Gbytes who subscribe to the small range of services. There's nothing free available. I suspect Three might even be getting a kickback from them. Otherwise it's pointless. I costs them nought to do it, where they have the spare capacity it works, where they don't, it won't, paying customers will be prioritised.
E.g. I have a Three mobile contract with unlimited everything, calls, texts and data (they even state that you could use 1 Terabyte/month, no problems). So "Go Binge" is irrelevant to me. I tether to my mobile and it generally works well. Though a dedicated router would be much better. £18/month on rolling 1 month contract (I've been with them for years).
I've been using it for years all around Europe and being careful with my usage, never hit the data cap. Considering buying a Huawei B525 router and popping my SIM in, apparently the phone SIMs work in them.
The B525 has a connector for an ordinary landline phone, which you can use to make and receive phone calls using the mobile phone SIM as well. Or you can configure it as a SIP/VOIP phone using the infinite data instead.
Actually the router they supply in the package is capable of the same too, but Three in their wisdom have disabled it in their bespoke firmware. Missing a trick I think, if they offered a package that completely replaced home landline and broadband that would surely be more attractive. As it is even the unlimited everything phone contract is a few £ cheaper than the home broadband, and there are always offers, currently first six months half price.
Searching around for local SIMs at decent prices is a hassle, then registering them often requires proof of residence, maybe other ID checks, certainly in France. It's nothing like as easy as you might imagine if you haven't tried it.
Nothing like the UK where it is frankly ridiculous, anyone can just buy a disposable mobile for cash, a top-up card for cash, ten minutes later they are up and running, even roaming around the EU and further afield, our mobile rates are some of the lowest in the world, then get up to whatever dodgy activities. We are wide open, the networks don't care they just want the money, and it seems our legislators don't care either.
Not so elsewhere.