Vodafone has set 4GB as the absolute limit. Three, by comparison, offers up to 12GB of inclusive data with its all-you-can-eat data plans. To mitigate this, the network is emphasizing the geographical scale of its new scheme. Vodafone's inclusive roaming covers 40 nations, including France, Germany, Greece, Italy, Spain, the Netherlands and Cyprus. Three, meanwhile, offers 19 "Feel at Home" destinations at the moment.

The deal has been introduced ahead of new legislation, drawn up by the European Commission, which will scrap EU roaming charges altogether in 2017. A stop-gap measure was introduced last month, limiting the fees that network operators can enforce abroad. Vodafone's move isn't too surprising, then -- it had to offer such a scheme eventually. By introducing it now, the company can attract subscribers before the summer holidays, fortifying its market share before O2 and Three potentially join forces.

Here are the countries that Vodafone's inclusive roaming covers: Albania, Austria, Belgium, Bosnia and Herzegovina, Bulgaria, Channel Islands (Jersey & Guernsey), Croatia, Cyprus, Czech Republic, Denmark (including the Faroe Islands), Estonia, Finland, France (including Corsica), French Territories, Germany, Gibraltar, Greece, Hungary, Iceland, Isle of Man, Italy (including Vatican City), Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, The Netherlands, Norway, Poland, Portugal (including Azores & Madeira), Republic of Ireland, Romania, San Marino, Slovakia, Slovenia, Spain (including the Balearic Islands), Sweden, Switzerland and Turkey.