Suspension Knock

[snapdragon]

I have had noisy suspension since last summer with various rattles, creaks and crunches.
I have replaced all 8 arms with OE TRW ones and this has improved things dramatically. The old lower arms had done 210,000 miles and were still in pretty good shape.
I still have a double knocking sound, by double - I mean the knock always comes in quick successive pairs like some free-play to and fro.
It is over small bumps and imperfections, not big bumps. I can't feel any play in the tie rods or when steering side to side. (The tie rods are original too - pretty impressive quality)

I am now wondering if the air dampers could be noisy or if it could be the top mounts. On these cars, the damper doesn't really swivel with the strut/hub when you steer like on many other VAG cars, so as far as I can see no top bearing mount, just a big rubber bush that looks OK. I also wonder if it could be the steering rack or inner tie rods?

Any thoughts would be appreciated as it spoils the enjoyment of the car.