We made the decision (regrettably now) to fly from Chicago to Dublin then fly from Dublin to London immediately after. How long should we allow between arriving in Dublin to the flight from Dublin to London?
Are you regretful because you now want to see something of Dublin, or another reason? If you haven't booked your Dublin to London flight yet, is it possible to make it sufficiently later so that you can experience Dublin a bit?
What airline are you planning to use? Heads up on Ryan Air that they charge for printing your boarding pass at the airport unless you have the business fare.
AirLingus
One ticket or two?
Do note you will go through immigration in Dublin and not in London.