Roaming charges aren't something you should be worrying about on holiday, as most major UK carriers are well aware. Vodafone will let you use your usual call, text and data allowances abroad for as little as £2, while Three lets you do the same for absolutely nothing. After falling behind the curve somewhat, O2's now updated its Travel tariff to make roaming more attractive, leaving EE as the only network still following the old-school megabytes-for-money package model. For £1.99 per day, pay-monthly O2 customers can take advantage of unlimited data roaming across Europe, as well as favourable call and text rates. Pay-as-you-go customers can also purchase the travel bundle, but will only get 50MB of data each day. While it is truly unlimited for contract holders, O2's fair use policy means that after 100MB (or half that amount of streaming video/audio), your connection speeds will be throttled. Still, that's more than enough for checking email, using maps and posting the odd self-congratulatory Instagram snap.