I had no issues at all regarding my gender not matching my passport. The airline staff did not blink twice at boarding. The security staff were all lovely, calling me Miss and getting a female attendant to pat me after I set off the metal detector. (a million miles from the horror stories I heard from the TSA)
The passport control in Dublin went super smoothly too. Again the guy did not blink twice seeing my passport. I did not try the UK border control as the flight from Dublin is considered domestic. (not sure why not from the Irish authority’s point of view?)

Now the trip was not without issues as the flight was delayed on the way out and I faced a long waiting time on the way back to check in and to get my luggage back at Heathrow.