You can view costs for roaming in Croatia at https://ee.co.uk/help/help-new/roaming-costs/countries/croatia - this allows you to select your circumstances i.e. PAYG, pay-monthly etc
You may wish to consider the Roam Abroad pass - https://ee.co.uk/help/help-new/offers-and-services/passes/what-is-the-roam-abroad-pass
PAYG phones are auto-enabled for roaming, providing you've used the phone in the UK before.
Pay-monthly phones need to have international roaming enabled first, before they will work abroad.
