I just had a quick look at British Airways timetables - and they state between 3 hours 45 minutes to 4 hours as the flight time.

Qatar Airways

The straight-line distance from London, UK to Noord-Holland, Netherlands is 225.1 miles. This is equal in distance to 362.26 kilometers.

British Airways

There are many ways to do that. You could fly British Airways, Ghana Airlines, AfriqiyahAirways to England , or KLM to Holland, or Air Burkina to Paris. - Each of those European destinations has connecting flights to Ireland.