Only £160? you got off lightly.
For the European Luscombe Rally at the beginning of the month we needed an exemption from the CAA to allow us to drop flour bombs.
The exemption is a single page standard letter from the CAA detailing the date time and place of the event and the name of the person in charge. It is accompanied by a single sheet of guidelines.
The cost? A snip at 200 quid!
Difficult to see how you could viably run such an event. If you charged two quid a try that's 100 runs down the runway just to get the CAA fee back, the neighbours would have something to say about that!