Due to a restriction in the MATS Pt 2 VFR singles aren't allowed to transit the Gatwick ATZ, so unlikely to have been fixed wing VFR traffic waiting to cross the airfield. Don't shoot me for mentioning this particular rule please, I only apply them not make them.
More likely to have been some sort of survey flight or one of those operators that take photo's of houses then go door to door to try and flog them. These are not at all unusual.
WF.