A bit of local knowledge can help the decision making process.
The VOR 'en-route honey pot' has been mentioned but another consideration is instrument training. Airfields such as Stapleford and Shoreham are more likely to have IFR traffic holding in uncontrolled airspace above the ATZ. In these cases I would tend to make my presence known to the controller / FISO (unlikely to be A/G in this case).
In the specific case of the original poster, I would call up something like
"Goodwood Information, G-ABCD PA28 EGxx to EGyy, overhead Bognor 2000 ft, routing via your overhead for a short photographic detail over the airfield, request traffic information"
Alternatively, if while listening in it became obvious that the frequency and airfield were very busy, I might just keep quiet and route overhead at 5000ft, keeping a good look-out. It's always good to have a back-up plan.