Sim card for europe

Expensive.
Try the UK "3 feel at home" card.
Loaded with 12GB of data and can use in most common European countries.
Best price I got was from my memory in the UK.
Link below:
12 GB sim

Not a fan of the Three offering. I have the 12GB 12 months Sim in an unlocked EE device and tried to use it in France during the summer. No matter where I was and we did a nice bit of travel at best I was lucky to check email. You can banish any thoughts of streaming anything from it.
Having landed back home side by side with an Irish Three Sim the speed difference was massive. Haven't used it on the UK network but wonder what speeds I would get. Put a Vodafone Sim into the EE and all worked fine at home.

I had a similar problem in France and Spain this year after I put my iPad sim into a MiFi, turns out that as there was a restriction on the sim to block tethering from the iPad when roaming the sim being in a mifi made it appear as though it was tethering so stopped it working.

I am also a realist in that I can't expect to have the ability to stream while roaming because as a business model it isn't sustainable for any company to allow that sort of expense for no additional income! I am happy being able to access my email, surf the web and even make the odd Skype call as I'm on holiday and don't want to do what I do at home after all it's a big world to explore.