OK, I'm going to hold my hands up and say that I had a similar incident several years ago at PMI.
I was the FO at the time on an A320. Whilst on stand and being recatered, fuelled etc. the Captain was elsewhere - I believe in the jetty, but it doesn't matter. Whilst I was doing some paperwork on the flightdeck I noticed thick black smoke drifting past the windshield. I opened the DV window to see the source and it appeared to be coming from the back of our aircraft. I put out a Mayday call (the only Mayday I've ever made) then went into the cabin and got the girls and cleaners off via the jetty at the front of the a/c. I went outside to find the fire brigade already arriving on scene.
It transpired that a catering truck at the back of the a/c was the source. Apparently in some failures of a diesel engine they can start feeding off their own sump oil - it will do this until the engine seizes and the engine cannot be shutdown by normal means. This produces a large amount of smoke and there is a significant risk of fire. Anyway, the truck was towed away from our a/c and left until the engine seized and stopped - no damage to our a/c.
I fully support what the FO in the Stansted incident did - his actions should not be criticised in any way - IMHO. If anyone has ever seen (even the edited version of) the videos of the Bradford City football disaster you will appreciate the rapidity with which fire can spread - you cannot out run it!
Please don't underestimate the danger of fire anywhere near an a/c - it is my/our worst nightmare!
ATB
Underdog
(edited for typo)
[This message has been edited by Underdog (edited 06 July 2001).]