Speaking of Stonehenge, the most recent series of Doctor Who used it as a location for the final story of the series (The Pandorica Opens/The Big Bang), and most of that shoot was done at night.) So while TAR wasn't unique in filming there, it's very rare, and it was the latest world landmark to make some sort of appearance on TAR.
I'm not bothered that teams only got a clue at that locale; it's the seeing of it, and finding it by self-navigation and driving, that was the treat. The show has often sent teams to a world landmark on the first leg (1- Victoria Falls; 2- the Christ Statute overlooking Rio, 3- the pyramids outside Mexico City; etc. (And by sending the teams there out of Heathrow provided Phil and Bert the time to get to Eastnor Castle before the teams.)
The place was beautiful to see, and I'm glad the show went there.