It depends on what method of travel you are using. A flight would take about 1 hour. If you are driving, around 12 hours including the ferry crossing.
You can travel from London to Ireland by plane or by road/rail and then ferry.
You can fly or drive to a port and take a ferry
The Eurostar goes from Paris to London, it doesn't go to Dublin.
about an hour
it took a long time
If you took a bus from Dublin to London you would never get there because you would probably die. You see, Ireland is its own land mass and you can't drive to the United Kingdom. I would suggest you take a geography class prior to traveling.
5 hours
About 4.5 hours.
About 2 hours.
About 3 hours driving
About 3 hours by car.
39 minutes ... it is about 19 miles