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).
what about if crossing LAM VOR IFR in IMC, above ATZ and below TMA with cloud base at 1500 feet and therefore little transit traffic through stapleford ATZ. Would it then be appropriate to stay with RIS and remain clear of ATZ and perhaps keep a listening watch on COM2 to the AG. I would think that talking to AG in this situation clear above ATZ not necessary. Please correct me if wrong