Adrian - please talk with Tim Milward in the UK (
www.slotcars4u.net) - I believe Scalextric has gotten artwork from him in the past. He's got the definitive artwork already done for all cars but the yellow one.
As for the Historic T/A Series - VERY cool, but NOT authentic in most ways. The cars are heavily over-restored in some cases (1963 Falcon with flares anyone?) and do not always represent the cars as they ran in the day. Good generic liveries, but if you want a specific race, again Tim has done the research for the correct ones.
Either way, thanks for producing the Cougar!