Seat height adjustment motors

[malum]

Hello
I have an A4 cabriolet (2002 B6) with electric seats but seat height adjustment on the driver’s side only. Both the front and rear height adjustment motor assemblies have failed. The motors still work (I can hear them) but they are grinding away at nothing.
I'm assuming that they have stripped a cog.

I can't buy anything but the whole assemble from Audi (£245.50 each) and I can't find any second hand ones (presumably because they are flimsy as hell and fail)

I am waiting for the arrival of the correct triple square socket to get the seat out and have a look at the assemblies, but they look like they come apart.
My questions are:
Are there any user serviceable parts in there?
If so are they shared with any other motor assemblies which I might be able to get hold of?
could I have the busted part fabricated?
Has anyone taken one of these things apart?

The part numbers are
8E0 959 112 (fitted to right side of driver’s seat, moves rear of seat up and down) essential as my wife is 5 foot 2 and I am 6 foot 2
7L0 959 762 or 7L0 959 762b (fitted to left side of driver’s seat, moves front of seat up and down) This one isn’t essential but would be nice to have

Any help much appreciated

 

[malum]

Further to the above. I've taken it out and it does come apart. The bit that is faulty is a small ferris wheel shaped plastic wheel which is driven by a worm gear.
I don't know if any other VW/Audi motors share the same small plastic part though.

 

[malum]

In the end I found a second hand one (for the right hand side motor which was the vital one) it was £120 though.
I'm sure that the plastic wheel could be fabricated or cast with a little bit of time and patience, unfortunately I didn't have time to try and do this.
It was fairly easy to fit. Took about 40 minutes.