Happily,I can report the BAA's information staff are trained in body language.
A Sardinian woman asks if it is easy to find a taxi at Heathrow.The answer she gets is a cheery British thumbs up.(Very likely from one of the 900 cabbies who serve the airport on an averge day.)Immediately,she clonk the unfortunate man with her handbag for making such a devastatingly insulting suggestion.This is why,incidentally,it's not a very good idea to thumb a lift in Sardinia.