Is there still a bus from Canterbury to Preston?
No longer a terminating service, Now part of service 11, the same one that serves Plucks Gutter mentioned above, as well as the delightfully, if not humourously, named Wickhambreaux. From memory, the 11 also has a fair few tight corners and at least one reversing manouvre, mainly operated using double deckers. I've only been on it once, but I keep meaning to go back and check it's worth suggesting to Roger French.
fact being that Orpington isn't flagged up as the destination i,e. in larger letters.

Preston Bus 20780 / PN57 NFG