I don't think they will quote you in euros. The standard procedure (of all airlines) is to quote the price in the currency of the country of origin of the first flight. So a price UK-anywhere-UK will be quoted in GBP.
If you do the opposite, say IE-UK-IE, you will get the price quoted in euros.
If you buy a GBP ticket, your credit card company will convert the fare to your currency at their standard rate.
Last edited by ExXB; 7th May 2013 at 07:40.