Excellent question, Dick. I've had a look on the government sites, and cars only needed 'official' CO2 data from 2001, so that puts our babies out of the equation. However, if anyone wants to check their 'other' car, this link may help...
http://www.vcacarfueldata.org.uk/
I've also had a look at my newly acquired MOT gas test, but that merely gives a figure of 0.75%, which doesn't mean much to me!
I have a funny feeling that we'd at least qualify for the new £40 p.a charge if our tax was based on CO2...