Rob, thanks very much. I may go for a #4, although there seem to be issues with the jack plane and the block plane. I own two #5s, one from the late 60s, and one from about 1949, and they are excellent. I also have a pair of newer Stanley block planes of the old pattern, a high-angle and a low-angle, and they are both fine.
Stu, I'll look out for a good used one. Shipping on the eBay planes averages about $40, which is extortionate, and often more than the asking price for the plane. Planes offered in the local media are usually on a pick-up basis, and more reasonable all round. I have kept the original blades on all the used planes I have bought, although I have considered the purchase of a Veritas blade for some of my planes. Buying the thicker blade would usually mean that I had to file the mouth wider, which I am unwilling to do.
I looked in Canadian Tire for a #4, as I had seen on the internet that they were a source for the new Stanleys. Although they carry a lot of Stanley tools, they do not carry Stanley planes, and the tools manager told me they never have. I looked at the Chinese-made Mastercraft #4, and it had no frog adjuster, and an obviious twist to the sole, possibly as much as 1/16" corner to corner. I put it back.