It's probably my fault, but following the signs onto the A4 Bath Road it simply never occurs to me to have to re-enter the airport area to loop back round onto the Concorde-not-really-a-roundabout junction to get onto the M4 spur/M4/M25/M40!
Or the long way round via the A30/A312 to join at junction 3...
Hence I usually end up on the Colnbrook by-pass gazing up at the M25 as I pass underneath on my merry way to Slough to join the M4 at junction 5, then finally reach the M40 at Booker......
The one and only time I used the HEX, it was anything but reliable. Train failure and no idea from the Paddington folk as to when the next one would be running..... Then that 'long march' to T2.... Joy!!
Heathrow and its lousy infrastructure deserves all the kicking it gets, in my view.
By the way, will ba's new pride and joy have a long term car park of its own?