Renault Laguna III - 2.0dCI Sport Tourer Owner's Review - Gromit
The AA say a car has an economic life of 8 years. Joe Public would hardly reckon on getting more than 10 years out of a car.
So, this Goona is half-way through its life expectancy, and has developed a fault that may cost 1/10 the purchase price to fix, but is otherwise roadworthy. I don't think that meets the standard for 'not fit for purpose'.