It may need nothing more than replenishment of the EOLYS fluid. This is a small tank of fluid that is dosed into the fuel tank every time the car is filled with fuel. It can last anything from 30,000 - 80,000 miles, depending on how often the car is refuelled. You can get a £50.40 kit from www.auto-essentials.co.uk.

For tanks with the green filler cap you need the post-2002 EOLYS 176 / Infineum F7995 fluid. These are genuine PSA parts and do not come with instruction manuals because it is assumed that they will be used by a trained fitter. I wouldn't do the job myself, I would pay a garage to do it.