Best answer by terrywebbs
Not free it's just taken out of your monthly allowance, thats the way it reads to me anyway, once that expires you will be charged accordingly.
The following link should help you in your quest
https://www.idmobile.co.uk/help-and-advice/eu-roaming
Take note of the section about
What does your inclusive EU roaming plan include?
Receiving incoming calls and SMS from any country is included in your monthly allowance.This link will explain more about charges
https://www.idmobile.co.uk/help-and-advice/international-and-roaming-charges