The source code for the PIC12F683 is now available. Get it here: http://hastebin.com/ixenagoref.vhdl this is the code that julian uploaded a few years back. since his site is no longer up and these cant be purchased I uploaded it here. hopefully someone finds it useful. I plan I trying to make one sometime myself.
See diagram The solar panel (max 100W) connects to the anode of the 90SQ035 Schottky diode at the top right of the drawing. The positive connection of the 12V lead-acid battery connects to Vbatt – Note that Vbatt appears in two different locations on the drawing and 0v (zero volts) in a number of positions along the bottom. Vgate is is the high voltage generated by the charge pump.