[Rob J]

Your Renault seems to be the RS01 in the Polistil "Champion 175" series, cat. no. A115. The website www.policar.info describes it as a 1979 car, though that may apply to when it was issued more than the 1:1 car year. The RS01 raced from 1977 to early 1979 and, as driver#8 says, its body shape changed. It ran with a variety of aerofoils, air intakes, engine covers, radiator bodywork, etc, so perhaps don't worry if the first photos you find show a different-looking car.
Can't help you on development. I have the Wolf in the same series but haven't done anything with it. They are attractive little cars, but the motor is a rather feeble old cube and, as usual on Polistils, the tyres are poor.
You may find something by using the SlotForum search box (up to the right), but don't be confused by what people have done on the earlier Polistil series with cars like the McLaren M23, Tyrrell 005/006 and Lotus 76. They are bigger cars with can motors and their rear wheel-axle unit can be easily replaced by a Scalextric unit and decent tyres are easily available.
Enjoy your project.
Rob J

 

[Rob J]

There's a 2007 thread on these cars at http://www.slotforum.com/forums/index.php?showtopic=25886
The "air tyres" mentioned were on the following series, "F1 Professional", as was the guide behind the front axle.
If you're keen on chassis building, Danny, one possibility would be a sledge like the original but with new parts all round (or front to rear).
If the originator of the 2007 thread did build a new chassis, I can't find a post of it.

I think I'll leave my Wolf as it is, apart from the tyres. That's a good-looking group you have, Philip.
Rob J