Legal.
I'm pretty sure that no one would disagree with you regarding the G.A landing fees. It's my understanding that the airport was made PPR to non based operators so that all GA could be handled by the FBO Saxonair. Saxonair charge about £10 of the landing fee as their handling fee, the rest goes to Norwich Airport Ltd, so how the MD at Norwich can say (and this is only what I've been told) that they make no money out of GA landing fees is beyond me and a complete embarassment to everyone there.
Despite the rumour that the airport is allegedly in very very deep financial poo and many staff making very sensible suggestions about cutting fees to attract more GA, the people who run the place (Omniport/Norwich Airport Ltd) seem to have their head in the sand and allegedly simply refuse to listen.
As for the ADF, that's something that every commercial passenger at every airport in the UK pays - it's just that most squirrel it away into the "taxes & charges" part of your ticket costs. At least airports like Norwich, Liverpool, Newquay and a few others are honest enough to let you know about it.