Many times you can save money by connecting at another European gateway. Speaking of London, some airlines offer incredibly low fares from outlying airports such as Stansted. Keep in mind that you may have to change from one airport to another using surface transportation. This can be very trying especially when flying all night to the European gateway. The choice sometimes comes down to saving money by making connections, or choosing a non-stop flight for the convenience.
Ferries There are ferries from England, Wales, Scotland and Continental Europe to Ireland.
The ferries take autos as well as foot passengers. How long it takes will depend entirely on the ports you choose, the route you take and the type of ferry.