InterRail issued RoamingFree sim card with the phone number from the UK (+44?????) seems to me interesting
~>
InterRail <~
My favorite sim and VoIP for roaming in Europe and worldwide:
UWT-mobile and Xxsim: for call+sms in Europa extern and Worldwide
ToggleMobile: for internet+call+sms only in EU intern
(VoIP/Sip) FriendCaller or SipCall.ch: Worldwide sms+call