My back end has developed a loud creaking from the rear suspension, its not noticeable when driving only when i get out and the spring decompresses.

Bushes knackered?

Its a 2005 C5 Avant that has never had a tow bar fitted but everyone mentions that it looks as if it sits quite low.....so im assuming it has sports suspension fitted (its a final edition so could be fitted with all sorts tbh)