Originally Posted by alserire

Luggage will be checked through to LHR. Although I am not totally certain the following probably applies. The UK and Ireland are a common travel area. You arrive in LHR as a domestic passenger would. On that basis you will probably have to clear immigration in DUB, On that basis it's unlikely you'll have too much time for a lounge. There are two lounges but unless you're travelling in J class you'll have to pay to access them. You will not need to clear immigration in London but you will proceed through the customs channels there.