Ordinary residents of Ireland, UK and other EU member states can access necessary healthcare from the state healthcare systems in Ireland, UK and EU member states on presentation of a currently valid EHIC (European Health Insurance) card.
For UK residents, once your current EHIC card expires, you can apply for a new UK issued GHIC (Global Health Insurance Card). This entitles UK residents travelling in Ireland to access medically necessary state health services on the same basis as an Irish resident. You may still need to pay a fee for some services, like an Irish resident. You will not need to pay for hospital care including A&E or inpatient treatment, although you will pay in full for private healthcare.
'Necessary healthcare’ mean healthcare which becomes medically necessary during your stay, and you cannot reasonably wait until you’re back home to get it. This is not a replacement for travel insurance. We advise that you take out travel insurance and breakdown assistance before your trip. Not all state healthcare is free and free services may differ between countries.