Hi there!
That's amazing that you are coming over from the Land of the Rising Sun!
I'm not really familiar with connection times at London Heathrow, but I would suggest allowing time between both flights (at least a few hours), especially if you fly different airlines and have to collect your luggage and check it again. Connection times can vary (potential outbound delays, security and immigration checks for instance). Since you arrive in London early morning, I would
book a flight to Dublin in the early afternoon if you can.
Now, do you already have plans and ideas of places to visit in Ireland? Let me know if you need any suggestions. Our
trip ideas page is a great place to start planning your journey.
Talk soon,
Antoine