White Waltham for Heathrow
As a non-London resident the jammed-up motorways are useless to me as my car is parked a few hundred miles west. For central London access I'm usually landing at (friendly inexpensive) Denham and using public transport which means walking to Denham railway station (15mins) and getting the train to Marylebone (30mins), often with a travelcard.
Elstree is not walkable from Stanmore tube anything like as easily.
White Waltham to Heathrow has been a short and easy run on the odd occasion I have done it in a taxi. Nothing like as easy as Redhill to Gatwick, but I've never been snarled up on either journey - maybe I've just been lucky.
I tried Fairoaks once and after landing got a taxi to ?Woking railway station which also was not walkable.
Believe me, I've tried all the options including Battersea Heliport (before the price went crazy) and would favour Denham for London access and Redhill for Gatwick access followed by WW for Heathrow.
What really is priceless though is looking down on all the traffic as you slip out from under the London TMA on departure from the smoke.
London - great to visit - awful to live in IHMO,
SB