Shouldn't be the case Eddie - *all* camera installations are supposed to adhere to the code of practice - as I said before, this is because they are supposed to be a deterrent/reminder as well enforcement.
But they don't play fair - because they want/need to catch people to raise revenue - which is wrong. But hey, they make the rules, so they can break 'em.
[ and yes "if you stick to the speed limits you don't get trapped" - but who in this world is perfect? ]