Citreon xsara picasso rough down the gears

hi, recently bought a 2006 citreon xsara picasso 1.6 petrol. it has 32,000 miles on the clock and is an ex mobility car. everything is great but i've noticed that when i let my foot off the throttle and the revs start to die down the car starts to 'kangaroo'. dipping the clutch stops it and it seems to do it more in 3rd but does do it in every gear. the car isn't dying into a stall it's doing it at quite high revs. anyone have any idea's?