suspension knock? 123 series

[thebendz]

I finally decided to rectify the os front suspension knock my 123 series diesel has had since I bought it 6 months ago.
Three garages failed to find the source of the problem and as I cant detect any play anywhere with limited leverage of crowbar I began replacing parts!
Upper wishbone and bushes, lower wishbone bush (the one under spring plate). This made no difference whatsoever so I am now considering replacing the guide rod chasis mounting and wondered if anyone has had success with this and if it would produce a knock if worn?
Or.. could it be steering related, the arms seem ok?