Clio 172 Mk1 - 2000 - 2002 (March)
Full leather, Cable Throttle (Full fat)
Clio 172 Mk2 - 2002 - 2003
Full leather, FBW, updated induction system, few tweaks here and there (Full fat)
Clio 172 Cup
Cloth Interior, FBW, same engine as all the other 172's, Lighter, no Xenon Headlights, No ABS, Designed as a trackcar and is a very useful tool (Lightweight) No Spare Tyre.
Full leather, FBW, 4-2-1 Exhaust manifold and twin exit exhaust system with flat bootwell.
Clio 182 with Cup Pack
Wider Track, Same spoiler as 172 Cup Anthracite Wheels, different bolt spacing on struts.
Clio 182 Cup
Silver Wheels, not the same spoiler as 182 with cup packs, Same suspension struts as 172.
Clio 182 Trophy
Recaro Seats, Sachs Dampers with Remote reservoirs and Eibach Sportlines (IIRC), Cloth bench rear seats (Renault presumed most people would take them out.)
That is an outline. I gave the Roger Green at EVO loads of information about these cars, they were a few errors but they did a review of them a few months ago - see if you can find a copy.
In my opinion the 172 Cup is the one to go for. Spend £750 on Coilovers and get them set up and about £300 on the brakes and you will have a weapon. Seats and Harnesses would be the next thing along with stripping the interior.
They embarrass a lot of more expensive machinery on track if you drive them well.
How heavily modified is the one you have see, who did the work and what has it been used for.
You can pick up a 172 Cup for £5500 at the auctions, but be careful as the 172 was cheaper than the 172 and as such was purchased by some people who had a certain affinity towards hedges and the like.
I would give a 172 a major service, cam belt, etc and a complete re-build along with the 182 manifold and whatever else you can afford to put into it and run it on an OMEX. Cams make the biggest gains along with pistons, headwork can be expensive for relatively little gain. Inlet matching and good induction can see good gains along with the work we have done on using larger throttle bodies than standard without going to ITB's.
Hope this helps.