EE, so far in 4 years doing 5 moths in Europe I have been fine but I stay under the 15gb fair usage and use wifi where possible. The boss does the same with Three no problems so far ...
There blurb ...
Hi from EE. Great news, while you're in Spain you can use your plan minutes, texts and data allowances at no extra cost. Calls to countries outside the EU are £1.20 per min and texts 50p each. Other charges are the same as when you're in the UK.
For the best network coverage your handset must automatically select a network. To do this, choose your phone from:
http://ee.co.uk/help/phones-and-device next select 'Connectivity' then 'Selecting Network'
While in the EU you must comply with EE's roaming fair use policy, including having a stable link to the UK. So, during any four month period you must spend at least two months in the UK or use your inclusive roaming allowances mainly while in the UK. For more info see ee.co.uk/fairuse.
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The bit that says your handset must be on automatic network selection is new !!! I did come of it once in Portugal and choose another. Bill was the same.
I also get streaming on certain channels Netflix, Prime, BBC Iplayer and that’s unlimited, no problems with this either ...