'He used to call her... Bessie.'
While not canon as it is an audio drama, The Paradise Of Death, written by Barry Letts, chronologically speaking is set between The Time Warrior and Invasion Of The Dinosaurs. Sarah Jane Smith became part of the Whoinverse in The Time Warrior, a story which in no way featured or made any mention whatsoever of the Doctor's car, Bessie. So how is it that Sarah Jane knows the name of the Doctor's car?
Excerpted from http://dwtpscripts.tripod.com/audio/rd03/rd032.html
JEREMY: Did you know him well?
SARAH: Not all that well. But he was a good man. And a brave one. It's silly, I know, but I feel as if I'd lost my best friend.
JEREMY: I don't think it's silly at all.
SARAH: Oh, you're very sweet Jeremy. Oh, this is no good. Life must go on, he'd want it to. We'd better go back to the office and get these pics developed.
JEREMY: Oh look, there's that Brigadier chap.
JEREMY: There, sitting in that little old car, the yellow one, talking on the phone.
SARAH: Oh, that's the Doctor's car. He calls... he used to call her... Bessie.
So there you have it. Three possible explanations spring to mind:
1. Metropolitan Magazine Investigative Reporter Sarah Jane Smith, prior to posing as her aunt, educated herself about UNIT's unpaid scientific advisor before her first encounter with him in The Time Warrior.
2. We sometimes hear the Doctor and his companions discuss places and events we don't witness on-screen but those places and events become canon by virtue of dialogue, no? So Sarah's knowledge of Bessie could well have been imparted to her by the Doctor after The Time Warrior and before The Paradise Of Death.
3. It ain't canon no matter what, so stuff it and move on.
Despite or perhaps because of questionable continuity, this particular story doesn't suffer. There are times when nostalgia trumps neat and tidy. This is one of those times. I highly recommend The Paradise Of Death. With a well rounded cast which reunites former TV characters including the Third Doctor, Sarah Jane Smith and the Brigadier, you'll hear other familiar voices... a personal favorite of mine, Peter Miles, plays a baddie like only he can. First broadcast in 1993, just 3 years before the death of Jon Pertwee, he reprised the role of the Doctor without losing a step, in top form some 20 years after leaving the role.
PRODUCTION NOTES: The Doctor — Jon Pertwee, Brigadier Lethbridge-Stewart — Nicholas Courtney, Sarah Jane Smith — Elisabeth Sladen, Jeremy Fitzoliver — Richard Pearce, Freeth — Harold Innocent, Tragan — Peter Miles, President — Maurice Denham, Onya — Jane Slavin, Grebber/Reporter — Brian Hall, Clorinda/Sec Gen of the UN — Jillie Meers, General Commanding Unit — John Hardwood, Odun/Patrol Leader — John Fleming, Captain Waldo Rudley — Jonathan Tafler, Greckle — Emma Myant, Rasco Heldal — Michael Onslow, Medan/Hunter — David Holt, Yallett/Officer of the day — Philip Anthony, Crestin/Bill/Radio Voice/Ambulance Man/Man - Andrew Wincott, Nobby/Kitson/Wilkins/Soldier - Dominic Letts, Echolocation Operator/Lexhan - Julian Rhind-Tutt, Kaido/Guard 2/Ungar/Custodian of Data Store/Jenhegger - Trevor Martin.
Writer: Barry Letts; Director: Phil Clarke