I don't know if it is quoted in any sort of British Standard somewhere, but here in England it is also accepted convention that hot is on the left, cold on the right. You do sometimes find a tub or basin plumbed in reverse though.
We should also spare a thought for the blind or partially sighted who cannot see the C and H markings.
Other related trivia:
Some old color-coded British faucets used green and red, rather than the blue and red which is now standard.
On older French faucets with letters, the one marked C is the hot (Chaud). The cold one if marked F (Froid).
