I had two weeks in the Vendee in June. You can just use your normal UK allowances, and the coverage is good. Since June 15th all data roaming in the EU countries, is the same as at home (for now until we Brexit)
My other half is on 3 so uses his phone as normal, but I am with Virgin (who twin up with Orange), and have no problem using my phone in Europe. I just turn off data roaming, but calls and texts are absolutely fine. The prices have come down immensely from 25p a text to just 5p now.
Next year, I...