After spending a week in London, I will be taking my granddaughter to Heathrow on May 27 for a flight back to the US. Her flight leaves at 3:40 pm from Terminal 5, and I had planned to get her to the airport 2-3 hours in advance, because of the Bank Holiday. Is this realistic, or should I plan more/less time? I have already purchased tickets for the Heathrow Express; can anyone give me insight as to whether they run a different schedule on that day? Thanks in advance.

Thank you, Historytraveler. I have checked timetables, and I guess I will have to continue to look for updated information as the time gets closer to when we leave. It's good to know that they probably won't have different service that day.