I finally got around to hacking a Philips SPC 900 to enable it to take long exposure images suitable for astrophotography. The modifications are fairly well known. The approach I took is a mixture of the http://www.boltonastro.org.uk/Members%5FArea/Projects/spc880conversion.pdf from Bolton Astronomical Society and http://www.yesyes.info/index.php/diy/philips-spc900-webcam-lx-and-ampoff-mod/ .
The circuit between both approaches is roughly the same, I followed the circuit in the former. The modification allows the camera to be switched to a long exposure mode via a switch. The switch can be triggered over a serial port, so I added a USB to serial adaptor and a USB hub (both from ebay) to the unit to allow control from a computer and have just one cable coming from the unit.
As soon as you have some new astronomy kit to try out it inevitably becomes overcast, so no test images just yet however I’ve included some images of the construction.