Gordon,
I reckon that there are two types of headlight switch. Both feature a rheostat action for dimming the dash lights. One has eight pins and a brown plastic base; the other has nine, larger (normal) sized pins and a black plastic base. This latter bears part number 1350151.3. There is also a difference in the "throw" of the switch itself and the screwed bezel is of a larger diameter. Which one do you require? I have one spare of each type.
Regards,
John Renaudon