This appears quite simple - a torsion bar acting as an anti-roll bar and supported by a separate spring and damper.
The suspension is not adjustable - so if the rear wheels have a wrong camber or toe then it is likely that the assembly has been bent and will require replacement.
However a recent check shows that one of the back springs is rusty.
The yellow car had lost both rear bump stops.
Just lever the remains off - it will break the plastic housing which simply pushes into the hole in the chassis.
The new bump stop simply clicks into place and is retained by the central plastic peg.
The shiny black is a coating of Waxoyl.
The fibre inner mudguard (item 16 in the drawing) is quite flexible and is held in place by 5 push-pin retainers - two behind the wheel; one low down at the front end and two others underneath at the very rear of the car.
The push-pins can be a bit sticky to get out so once they are on the move a simple trim removing tool and/or angle-nosed pliers can be used to lever them out. Wash to remove all dirt and they should go back easily.
The two push-pins at the rear were a bit fiddly to replace: Pin1 pushes in upwards (as would be expected) . . . . .
. . . . . and Pin2 has to be inserted from above. Line the holes up carefully and they go together easily.
First picture shows how it looks with the fibre mudguard, coil spring and damper removed. The spring is held in place purely by spring pressure and the smaller turns at the end of the spring locate securely top and bottom. Be careful when reassembling to ensure that the spring seats properly on the top and bottom contoured rubber cushions.
Second picture shows the simple spring compressors I used - be VERY careful as these springs are definitely slippery customers and the jaws can slide down the spring. Best for me were this pair of old compressors which with their relatively narrow jaws, maintained a safe grip on the turns of the coil.
It is so easy to mark the springs through to the metal that I waxoyled the springs to minimise future corrosion.