Update: picked up my brand spanking blue 172 on Friday - bloody excellent despite me not taking it past 3000rpm, it just seems to gain speed so effortlessly. Cant wait til it frees up then I can really give it a proper drive! Already managed to attract the attention of a couple of tits in a nedded Corsa who wanted a race - no chance, Im not interested guys. Must have been a 1.0 L because he had to rev the arse off it to get past despite me taking it easy.
And Ive successfully fitted a rear-mounted bike carrier to it already. I picked up a Halfords High Mount Deluxe rack for £60 (down from £130). It fits using plastic dumbell things that you stick through top of the tailgate - they pull against the inside of the tailgate/roof and dont put any pressure on the spolier (the spoiler prevents normal clips to be used). The rack sits on foam pads, one set against the centre of the back window, the other just on the bottom edge of the number plate recess. There are 4 other clips: 1 either side of the bootlid, 1 hooking through the towing eye, and 1 hooking into a hole on the chassis just to the side of the exhaust. Its also high enough so that it doesnt obscure the lights/number plate.
So if anyones struggling to find a rack to fit their Clio (any variety), it can be done (despite Halfords, numerous rack companies, Thule, and the local Renault dealer all telling me otherwise).