EU nationals do not require a passport as long as they carry an ID card (a driver’s licence will suffice for Brits). EU nationals also do not require a visa for stays up to 90 days. Visas for longer stays are normally granted to EU or US citizens without too much bother; you can contact the Irish Embassy for details:
Embassy of the Republic of Ireland 17 Grosvenor Place London SW1X 7HR.
Passport & Visa Sections Montpelier House 106 Brompton Road London SW3. Tel: (020) 7 235 2171 Fax: (020) 7 245 6961 Passports – Tel: (020) 7 245 9033 Fax: (020) 7245 6910.
British representation is unlikely to be required in Ireland but, if you need it, you can find the Embassy at:
29 Merrion Road
Dublin 4 Tel: +  205 3822 / 3700 Fax: +  205 3890 email: email@example.com