Basically internet/data while roaming only works when
Otherwise (i.e. any other membership or destination) it does not work.
If you are roaming in the EU on a Guido membership and find that it does not work then check your internet/APN settings and if the APN Type field has changed from "48months.liffeytelecom.com" then change it back to that, enable and then disable airplane mode and check if it works now.
Hope this helps.