There is no distinction between commerical or non-commercial. Loosely speaking if you are IFR and over 2T or VFR and over 5.7T you are charged at the NERL unit rate, which is the
second highest in the world.
Sorry, should have been clearer, I meant commercial in the sense of money changing hands between operator and ANSP, I am aware they can be non-commercial flights.
If you want to dispute them, you have to go to the CAA who set the charges, not NATS.
Where did you get NSL from? Stansted's Approach Radar services are provided by NATS Airspace, which is economically regulated by the CAA. Stansted's Tower services are provided by NATS Airports under contract to Stansted Airport.
Anyway, I've lost track of what your point is here. Stansted is inside CAS. LARS services around the outside of the CTR is provided by Farnborough LARS (NATS Airspace - mostly), so that's what you're paying for with that charge.
Maybe you should set up your own ANSP and start tendering for contracts SH.
