Originally Posted by G-BOAC
According to my mate who lives in East Croydon (don't worry, I make him visit me for drinks, I don't venture that way
) East Croydon -> Victoria -> Paddo -> HEX is the best bet.
It's not THAT bad here!!!
I've done all the aforementioned options more than once and train to Clapham Junc, then train to Feltham, then 285 to Hatton X, then rail replacement to T4 will be the quickest on 9 out of 10 journeys beating the HEX route by a few minutes.
Fastest of all would be to get a cab from Feltham station to LHR T4 - this should only cost a few £ and will save the hassle of the bus change at Hatton X.