Mk1 172s were replaced with Mk2 172s. This meant Mk1 172s lost value.
Mk2 172s were replaced with 182s. this meant Mk2s lost value
182s replaced with New RenaultSport model - mean 182 loses value.
Every car that superceeds the 182 will depreciate it bit by bit. I would say that if a 182 is worth £5,000 to £6,000 at the end of 3 years then youll be lucky.
My Clio Cup 172, as fab as it was, all fully kitted out, looking the business on a late-2002 plate was worth just £6000. I eventually haggled it £6,500 with the insurance company but that was stretching the limits tbh. I was really lucky.
There are alot of other performance hot hatches which will hold their value alot bettr than a 172/182 etc, so I would recommend looking around before splashing your cash.
CC.