Rear driverside wheel bouncing and knocking

did they check the damper?

yes sounds like the shock absorber also make sure the tyre is truly round ( no bulges or tread pattern parting)

Just to add to other posts , coil spring o.k ?

he only checked trailing arms and wheel bearings, tire is fine,

then its worth checking the damper.

this vechicle is torsion bar does not have a coil spring on the rear some times the axle mounts split not easely seen but worth a look not that hard to replace as said by the others before is that fat shock unit working ok, you need to remove it to test as this type of set up keeps pressure on when lifted so may look ok but kaput also check coil spring on FRONT LEG as could be snapped and shocks transmitting to the rear to look at may seem ok check top coil and bottom coil seen many snapped in these places

My partner had the same problem on her 52 plate 206. If you don't jack the car up try pushing and pulling at the wheel while the car is on the ground to check for play. I found there was a load of play on the rear arm when I was told to try this. Much more than the other side. It appears that when the car is jacked up the weight of the suspension pulling down on the arm is enough to "hide" any play in the bushes.
It appears this is quite a common fault on 206 rear suspension.
Hope this helps.
Ray

sounds like you need replacement trailing arm bearings which are available and easy to replace via a garage of course cost arond £30 for the btrailing arm bearings

thats how a found some play on the trailing arm when the car was on the ground rocking the wheel. i told the garage and they had it lifted with all four wheels off the floor, they checked trailing arms with metal bar for movement and cudnt find non

you dont need a metal bar to check for play in trailing arm! If car is in air just pulling the wheel is enough to find any play. you can also normally see there is a problem by the way the car sits on the ground. I would forget replacing just the bearing as everything will be seized and the axle tube will probably be worn also. A reconditioned axle can be purchased for approx £350 and would be a more cost effective repair.