Having just fitted the front hubs I cant seem to tighten the nuts on the top and bottom ball joints. They just spin around, I am doing something wrong?

Put a lever in underneath to put pressure on the taper to stop the threaded part turning and that should sort it.
Steve.

Sorry Steve, I'm not sure what you mean.

Push the treaded bar into the housing?

Sorry my description is a bit vague,
To stop the pin turning you need to put wieght on the taper, so you need to find a way of pushing the hub part down on to taper by leaverage or putting a jack under it,
Is that any clearer?

Steve.

Find a plain nut and tighten it up with that first to lock the taper, then use the nyloc to secure it. If you are going to be taking it apart and just trial fitting leave the plain nut on till you are finished.