The single engines jobs you see orbiting near LGW are photo/survey flights (Being called 'Survey32' or something similar kind of gives it away)
We do quite often get single engined aircraft landing at LGW; slot minders, a/c spares delivery, and the exec Pilatus types too. Can't clame to have seen a Cessna though, as they do tend to be Pipers.
As for routing thro' the ATZ:
Above 2.5A, you're into TMA Class A airspace, (no VFR)
Standard missed approach is straight ahead to 3A. (Local noise restrictions pressure us into not deviating from standard ops.)
So if an aircraft is going over the top not above 2A, one goes around straight ahead to 3A, VFR pilot busy sightseeing (no offence, I've seen the heli boys slow to have a good look at the holding point) IFR can't turn off the NPR but does outclimb the crosser.....and the VFR crew get flipped in his vortex. Not a good day all round really.
VFR tunnels may work at some units, but until its proven to be safe, noise friendly and VFR not hindering IFR traffic, then it'll be round the ATZ I'm afraidl
