Hi,
..what protection do I need between a 12v signal from the switch and the picaxe input pin to detect activation of switch ...?
Yes, about 22k in series is about right, it will limit the current to less than 1 mA when the internal "electrostatic protection" diode(s) on the pin "catches" the voltage to the supply rail (or to between the supply rails). However, there are a few "gotchas":
Firstly, the "Input only" pin (usually Leg 4 on M2s) does NOT have a catching diode, so you must be add an external diode if using that pin with a higher voltage input.
Secondly, current flowing into the protection diodes can "phantom power" the PICaxe (which itself only drains about 0.5 mA). Normally, a "series" regulator can only feed voltage
into the PICaxe rail (i.e. up to the required 5 volts), it cannot shunt away any additional current coming into the supply rail from elsewhere. So if several inputs might be activated (high) at the same time, then you may need to add some additional drain to the supply rail. A shunt "zener diode" is often recommended but IMHO is nearly always a poor (and probably unsatisfactory) choice. A simpler solution (as implied by lbenson) would be to add a 10k resistor from each input to ground, forming a potential divider (10 / 32), much in the way the programming input is NOT supposed to be connected !
Cheers, Alan.