Hi Brian and All,
The consequences of fire damage dont bear thinking about

Brian, the fire training really pays off!!
As you said the extinguisher only subdued the fire and you were able to remove the "fuel source"
When I had a job in the powerplant Industry we used to do regular fire training like you
You soon learn that one extinguisher is pretty useless in a lot of situations, and certainly the mickymouse ones should not be relied on

In the workplace I was in, any welding / cutting /grinding outside the workshop welding bay had to be done under a
"Hot work permit"
This required a "Risk Assesment" beforehand and depending on location several post work inspections or a body staying there for a specified time as watchman!
The latter especially applied to coal /oil fired power plant
At my own place I am very cautious regarding fire and have recently moved all the bikes to a separate new building
(tanks drained!!)
only the bike being worked on is in the workshop. I keep an old workmate outside for grinding operations

I try not to start any bikes inside especially "unknown quantities"
I have 2, 20lb dry powder extinguisher's and a CO2 one + a fire blanket in the workshop
and am still uneasy

With Fire Prevention paranoia is essential

Glad that you and your bikes escaped relatively unhurt

Best Regards
John O R