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).
Ok but one presumes the commanders of these aircraft are ensuring that an adequate lookout is being maintained in VFR or if VFR cannot be maintained that they are in receipt of RIS if possible?