I will be staying at the DoubleTree/Hilton in Kensington. I will need to catch a 10:30 AM flight from Heathrow (BA) on a Wednesday morning and wonder the best (quickest/cheapest) way to go. Would appreciate your advice. Many thanks! BP
If you can book far enough ahead, Heathrow Express tickets are reasonable. Take cab to Paddington station from your hotel.
Usually 'quickest' and 'cheapest' are mutually exclusive.
You can also pick up the Piccadilly line at the South Kensington station. It seems to be about the same distance from your hotel as the Gloucester station. Just ensure you get the train to the airport.
I believe the Tube starts running around 4 or 5am. I'd take it from S.Kensington to Heathrow Terminal 5(if that's your terminal. Look on the train front to see where the train destination is. Since you are doing a reverse commute, the Tube shouldn't be too bad.
Thanks to everyone for your input and advice. Good stuff! BP
Here's the interactive planner for London transportation, to check times, expected duration, etc:
Google maps is getting better at charting public transport too.