I seem to remember these approaches into LHR aswell during the 80's and early 90's. They were mainly BA B757's. I lived in Southall, not too far from the gasworks at the time. They looked as if they were over ealing. I also recall a few that appeared to come over my house aswell but were not following the 23 extended line. I think I recall B757's, DC9's, B737's and MD80's flying these approaches. I always assumed they were aircraft being slotted in after a go around. I dont think i've seen the approaches performed for over 14yrs or so.