Wouldn't imagine there's any difference in reliablility between a 172 and 182. Love my 172 but if I'd been able to find a 182 for the cash I paid for the 172 I'd have gone for a 182 just for the twin exhaust.
As far as reliability they aren't bad cars at all and most parts are pretty cheap to replace and the for sale section can usually sort you out for not too much. If you've got any practical skill at all you can do a fair bit of servicing yourself (oil, sparks, filters, brakes, pads, interior bits etc)
Mines been no real bother except for the usual random warning lights for no apparent reason and other bits needing replacing as you would expect on any car.
There's a guide for buying a second hand clio on here so give that a read before you go kicking tyres or buy a dog.