(This doesn't look to be symmetric, for some reason--if you're a Three customer in one of those countries I don't think you avoid roaming charges in the UK.)
Three customers in Italy had the no-extra-charge-when-roaming feature already 4-5 years ago actually. That was both for data and voice. http://www.tre.it/opzioni/estero/all-estero-come-a-casa EDIT: I see there was a bit of overhead actually. not quite the same tariff.
