Sore point for some of us in the UK.

Tax goes to the government and is essentially the same for all departure points at the moment. (There are a few oddities).

Airport charges are what makes the difference and this money doesn't go to the government.

From Amadeus:
UK Passenger Service Charge (UB) – A charge imposed by airlines to cover costs they pay to airports for the passenger to use the airport’s amenities and services. This amount varies from airport to airport.