"Take your UK plan with you and Feel At Home in seven other countries around the world.
With Feel At Home, you can call or and text the UK and get online, using your current plan, in seven other countries, just like you would at home and it won’t cost a penny more. So now you can chat to your family, text your friends, post gloaty status updates and share your holiday snaps whenever you like, with no more worrying about extra charges on your bill.
Who can use Feel At Home?
Feel At Home is available to any Three customer - all Pay Monthly phone customers, SIM plans, Pay As You Go, Mobile Broadband and Business customers.
Which countries are included?
As a Three customer, you can call and text the UK and get online when in Austria, Australia, Denmark, Hong Kong, Italy, the Republic of Ireland and Sweden — just like you do at home.
So why not have a natter from Naples, send a message from Milan or even surf in Perth, without the worry of any extra charges? Just remember, if you send texts or make calls to local numbers while abroad you’ll be charged our normal roaming rates.
What do I need to use Feel At Home?
You don’t need to do a thing. It all happens automatically as soon as you arrive in an eligible country. Just wait for your phone to pick up any local mobile network and you’re good to go."
http://www.three.co.uk/Discover/Phones/Feel_At_Home