Check out the following link to find a list of every UK airport and the facilities it has on offer – http://www.airportguides.co.uk/airport-list.html
As an EA, you’re going to use hundreds of airlines depending on who gives you the best deal. Check out https://www.skyscanner.net for a list of available flights for your particular journey.
Below are some quick links to access the websites of main airlines you might use. Here you can check in online, manage your booking or just find out details about the airline and its terms.
https://www.tuiholidays.ie/flight/ (TUI Airways Ireland)