That is not the drop-link. The drop-link is the larger bar to the front of the bottom photo. That link looks like it connects to an electrical device that looks like it could be part of the VSA mechanism.
Are you sure that is the part that is knocking? It is far more likely to be the drop-link between the wishbone and the anti-roll bar that is knocking.
I agree. It looks like a linkage to some sort of roll or yaw sensor, I don't think any UK spec cars have these fitted - the bottom arms don't even have the bracket for the linkage. Probably a Fit RS specific device.
I also agree 100% about the drop link. 9 times out of 10, knocks on bumps are from the droplinks - because they go quite forcibly from extension to compression, and the tiniest bit of play (often undetectable by hand) makes them knock through the chassis.
The sensor linkage is very unlikely to have much tension on it, and I doubt that any play would sound knocky.