If you find that your wipers and mechanism are making funny noises it may be that the Wiper Drive mount is worn and probably broken. A tell-tell sign of this is the bonnet catching the wiper arms as you lift it. Thanks to Serena's guide on how to get at and dismantle the wiper drive linkages, decided to tackle it myself but hit some unforeseen snags. Magically this may actually turn out to be a bonus!
I had the drivers side wiper knocking on the top of the bonnet when in use and would catch if I lifted the bonnet up. So in short I removed the trim as described previously by Serena, undid the two retaining bolt and popped the end linkage off of the passenger side drive. Upon removal I was greeted with this:

Looking a bit worse for wear. The drive housing was pretty knackered and broken leading the whole arm to twist and bend out of shape, making it knock on the bonnet.
Not to worry, I'd sourced another one previously (and scored a brand new end linkage to go with it). Was literally about to fit it when found out the end locating ball joint was on the wrong side!?! Everything else was identical, so, decided to take things apart and see what could be done (rather than the sensible thing of putting it back together so I could actually drive the car legally)
In effect the rotating arm is held in the aluminium housing by a spring clip which is no doubt hidden in a load of grime and corrosion. It's located just below the splines and sits on the flat washer butted against the housing. Try and spot it in the image above!!!
It's a fiddly beggar to get off, but you can squeeze the arm up in to the housing (courtesy of a sprung washer at the back) to give you a little extra clearance on the spline end. Once you manage to get the spring clip off the washer comes away and the whole shaft can then be pushed back through the housing. It get's a little stiff as there is a rubber grommet in there, but it will go through. You'll end up with this:

From left to right:
- Shaft and arm (with rubber guard for linkage ball joint)
- Sprung washer
- Aluminium Housing
- Rubber grommet
- Washer
- Spring Clip
The replacement drive I got was in excellent condition, but the ball joint was a little off:

It was listed as a 323f, I'm guessing it was a saloon or the P version maybe, no idea. But at least the hosing was identical:

You can see the corrosion, damage and wear on my original one
So, a clean up of my arm and pretty straight forward reassembly resulted in this:

Now what this means is hopefully we can source drive housings from other cars that match and simply change the shaft and arm over to fit the BA. The shaft is hard steel whilst the housing is ali, so guess which is going to lose in the wearing out stakes! Mine was a bit corroded inside so sanded the shaft back and generally lub'd prior to putting back together

Oh, and grease the ball joint before putting linkage back on too
Now, my wipers work properly again and don't catch the bonnet anymore, yay!
Jon