Not very long ago the isolators on consumer units and the like was up for off and down for on.
Wylex had brown DP switches quite often.
Then the change in convention to down for off and up for on,
One popular belief that it was to algin with the continent and also in a panic then your arm throwing the switch down was easier/
Wylex introduced those new conventions with a red rocker switch.
I remember one chap returning a consumer unit (with Red Rocker) and the isolator was in bits, he`d found it "wrong" and opened it up in an attempt to fix it, all the bits flew out and he couldn`t get them back in! LOL.
But, as said, the old convention for lighting switches remained as was.
Speaking of conventions, using three core and e cable (I am a bit unusual in some things - If no one has noticed) many use the old red/new brown for com and the other two being blue/yellow or black grey , preferably oversleeved.
I am a bit odd, Red for L1, Yellow for L2 and Blue for Com, in new money substitute Brown, Black, Grey. Again all oversleeved ) leaving a small band as a witness of the original colour for easy reference.
I think logically it becomes Red (Brown) for perm L on three or twin and E cables. So a bit easier to follow at a glance but I do note that the other way of doing is more common and I can`t say it`s wrong. I just have my little quirks.
I did a house rewire for one lady who wanted all of the lightswitches in the up position for on and down for off but trying to explain to her that with two longish hallways and a couple of big bedrooms with multiple doors, that inevitably it could not be achieved because of some two, three and four way switching arrangements, so I did not quite win on that one.