Clive likely spends more time on two wheels in the rain than most of ever will. The only things I will ad is to make sure you have good tires, newer the better, after the first 100 kilometers that is, not going to start a brand discussion, keep the pledge on your helmet visor as well, rain-x does work better but be willing to swap visors once a year or so.
The biggest thing is to RELAX. Keep to speed limit and relax.
I ride year round, do not LIKE the rain but I do not let it stop me. If I did I would have less riding time than most of our southern and eastern friends.
Oh and buy a good rain suit.... I also have boot protectors, they are from a bicycle shop.