Could also try greasing the struts (the top bush can get a little dry):
Put it on high, pull the corrugated boot down, apply grease (not too
much) to the shaft, replace the boot and then run it up and down a
couple of times.

Knocking noises usually point to suspension joints. A famous one on the
Xant are the tie rods that connect each end of the anti-roll bar to the
struts (try holding the joint at each end and feel for movement while
your glamorous assistant rocks the car from side-to-side). Good news is
they're not too expensive from the likes of GSF and you won't need a
balljoint splitter to get them off.

Alan