Thankyou Zoltan,I have indeed and think you did a great job. It's a lot nicer than I could have ever managed.
I'm in the process of designing a MK2 version, having found a couple of issues that I'm not happy about.
I used gears that were salvaged from a laser printer gearbox that I was given. Unfortunately the gears that I chose, whilst fitted nicely have too high a reduction ratio and flat out at 30 volts, the drive is a little on the slow side. So I really need to make the motor spindle gear a little bigger. However I can't get the gear off the shaft without damaging the worm wheel.
So I went and got another windscreen wiper motor. I hadn't realised that you could get left and right handed ones ! Of course the new one is the opposite hand, otherwise very similar.
I've taken it apart for cleaning and re-lubricating. I've taken photographs of the insides. You can see what I was on about when I was saying that these don't like running backwards. The only thing that takes the thrust of the worm is the single ball used as a bearing at one end and a washer against the end of the sleeve bearing at the other.
I've used M4 hex cap screws to secure the cover plate back onto the gearbox housing after removing the connector and electrical bits.