My boarding school was about 30miles due west of Heathrow and a lot of the foreign students would take a black cab from LHR there, I dread to think what the cost was bearing in mind a 5mile cab ride on empty roads from my local town to my house is usually the wrong side of $35!

Incidentally if you fly Virgin Upper Class you get a free car service to anywhere in the country, one customer who lives in Aberdeen and is too tight to buy a domestic flight takes advantage of this when arriving in London. Probably around 450 miles