Internet access and communications in Europe

We will soon be heading off to Europe, travelling through a number of countries (mostly EU members but will probably include Croatia, Bosnia-Herzegovina and Montenegro). We are seeking advice as to the best and most cost effective way of maintaining commuications with friends and family while on the road. Our communication requirements include back to the UK and also to Australia. As far as equipment goes we have a 'matching' smartphone a tablet computer. Please could someone advise the best method/package/bundle/plan or whatever to keep in touch without risking a gigantic and unexpected bill at the completion of our travels.