Apparently the only situation you are allowed to go below 500AGL is for landing and takeoff and a low approach is neither.
What if you intend to land, but decide to go-around from 3 feet? Or once you pass 500 AGL you have to land 
So back to EDTY, really nice airport, great hotel, very pretty town. Highly recommended.
And of course you should charge for a low approach or T&G (when an airport would charge for a full stop circuit). You are using the circuit. How is that so different from landing as far as resource usage goes?
And a practice approach should also be charged in my view if you are blocking the approach for IFR that may be using it for real. That is what really annoys me at Gloucester - you can fly in from France, wanting the GPS approach and you can't get it as 400 schools are doing practice approaches.
Of course, if you are given a straight in approach and choose to fly the GPS or ILS that isn't getting in anyone's way. But I wouldn't announce it.
