During the day yesterday while the car was parked undercover I sprayed inside with an odor neutralising product I had to hand called No More Tobacco Smells. Don't try this at home. The smell of sour milk comingled with the tobacco deodoriser and turned the stench from sweaty socks to baby puke.
In the evening at home I tried the mega shampoo and wet vac session WX51TXR. Great results! I did 2 shampoos of the affected carpet using BioZet washing powder which is enzyme based in lukewarm water. Liberally brushed the soapy water into the carpet using a paint brush, left to soak for 30 minutes then spent 30 minutes vacuuming the water back out. Like I said, did it twice, and this morning only the vaguest smell of sour milk if you stick your nose right against the carpet.
It remains to be seen if the smell returns during the day today with the car windows up or when I can't avoid parking it in the Queensland summer sun. Fingers crossed.
As further insurance, I also intend to repeat the BioZet shampoo and wet vac another couple of times and I'm going to flush as much of the undercarpet floor area as I can with the enzyme-eating soapy water too as I discovered once the all-pervading nature of the smell was gone that it's in evidence in the crevices of some metal seams and from what I've read, if you don't get it all, you may as well not bother.
JDP1962, how did you get on?