Having experienced living in this area in the past I remember noticing the LHR outbounds more than LGW as many were long haul and slow climbers. Presumably they are vectored towards LGW before turning more to the east to avoid conflict with the Biggin inbounds. Also when traffic allows, eg mid-late evening when LHR arrivals start to reduce, sometimes LGW 26L outbounds on right turn out on northbound SIDs are vectored north early tracking towards just east of LHR and these may affect your area.