I've written articles for various monthly technical publications over the years. Of all the British publishers I've dealt with, the arrangement has generally been that the editor just accepts a manuscript and sends me a check for his calculated amount when it runs. All fairly informal, and I've never had any cause for complaint; in fact I've been treated well.
When I did some work for Popular Electronics (Gernsback, New York) a few years ago, I was quite surprised to get a contract to sign stating the amount they proposed to pay, exact details of copyright assignment, etc.
As I said, I've never had any problems here, but I can certainly see how the signed contracts would make things much easier if there ever were a dispute.
