You may remember a while back that Mandrake and I tried to change a ball joint on his Xantia - but all we succeeded in doing was mullering the castellations on the joint with his electric impact driver (hub on the car). It didn't have detectable play in it, but there is a clonk suggestive of play in it somewhere, so it may have to come out someday. Cue the stilsons I expect!!
This weekend I had to change both the joints on my 307. I've had one for the NS for over a year (it was an advisory on last year's MOT, and it's going in again tomorrow
), so strip the hub off (no brainer on the 307 as there's no way to get the arm / hub disconnected without unbolting from the strut anyway) and get it in the vice. Clean up and swing on the joint with breaker bar, and it fairly easily relented and easily unscrewed. Then I tackled the OS, thinking it would be easier given it's less in the water. Er no.... 
Clean up the joint and swing on it. Nothing. Add longer pole. Nothing. Apply impact driver (which Simon kindly left in my garage in anticipation of this job). Nothing 
Blimey it's tight! Apply heat, and then impact driver. Nothing. Hmm, not looking good! More heat, more hammering, more long poles, and just as I was about to give up (and applying about 1000 lb ft, wondering if the vice was going to rip out of the bench!) it let go 
It was then tight to screw out, and the thread on the joint was clearly damaged. Can't see that it's ever been changed, so it must have been poor from the factory - new joint did screw in, but it was tight all the way in.So that's 2 joints that have laughed at 450NM of impact driver. I'm looking forward to helping Simon get that one out of his car when the time comes.....
Oh, and the 307 STILL rattles - suspect it needs a new drop link
PS Haynes captures this pantomime in its inimitable way "Fit a deep socket to the joint, and unscrew it"
I fully expect that if it is the ball joint on the hub that I may have to find another 2nd hand hub... 
