We fly from Dublin to London in June and are continuing on to Stratford-on-Avon by train. Which airport would be best in London to use? Stamsted(STN), or Luton(LTN), or Gatwick(LGW) Heathrow not an option on Ryanair.
Why are you flying to London? The nearest airport to Stratford on Avon is Birminhgam International, which has several daily flights from Dublin by both Aer Lingus and Ryanair.
Luton airport is the most centrally located of the three options... and it is the most central by a vast margin. I am assuming that you will fly to London for a reason here.
Public transport is a possibility to/from Luton, whereas Stanstead and Gatwick are well outside of the city and require either a train or an airport bus. Gatwick is minimum one hour by bus to London city center, and Stanstead is even further. The trains can get you to/from Gatwick in about thirty minutes, and a little longer to Stanstead.