I noticed on ebay a UK HAM has a Rotator Computer Interface for sale. It is quite an old model with parallel port control and looks to have been home assembled.

Photos on ebay:

http://www.ebay.com/itm/EA4TX-ARS-Antenna-Rotator-system-controller-wired-fo...

Info from manufacturer:

http://www.ea4tx.com/download/download-ars-manuals/

It seems to be RCI-SE Board which was sold from 2002 till End-2011. It seems to be PIC or similar microcontroller operated, rather than the newer USB arduino version.

I don't know the seller but someone here might be glad of the tip.