I can think of one word : HEATHROW.
For some reason , London airports Heathrow and Gatwick charge very high fees and this is passed onto the passenger.
International overseas taxes are also double that of international European taxes . But enjoy the 'lower' rates when you can. I understand that the international fees are set to raise even higher in the next few years.
Well, someone has got to pay for the 5th Terminal at Heathrow!