After much googling I've still not found what I'm looking for, so wonder if anyone here knows of any possible sources please? I want a cheap weatherproof box to contain a low voltage transformer, mains socket, timer, etc, for my pond light and pump setup. About 12" x 10" x 8" should be adequate, but bigger is no problem as I can hide it behind some plants. I'll drill holes for getting the various cables in (and maybe use cable glands to keep these waterproof, if I can't improvise something myself).
If it comes to it, I suppose I could make one myself, although I'm not confident of sealing the lid completely.