I think I learned my lesson over Christmas. It's too much of a pain and $$ to take HEX-taxi-train to kent from LHR. I'm headed back in a few weeks and will just hop on the underground and take the Piccadilly line all the way to Kings Cross and walk over to the St Pancras train platforms to get my single unrestricted to Ashford Int'l.
What I do find annoying is even though I can buy my train ticket online I still need to go the vending machine (what one of maybe 3??) to get my ticket again. Half-....
Regarding the tube I can't remember the last time I bought a ticket from the vending machine. it's zoned right? Is it pretty painless? I get angst because I know there will be impatient travelers behind me that use it everyday. It's no different when I lived in Chicago and was lined up behind tourists trying to buy el tickets via the machine LOL