Thank you. A problem with a lot of this is that basic users, who only use/understand the facilities to the level they need to, would not know things like this. All I know/remember is that I repeatedly got messages from BT saying that I HAD to switch by a particular (imminent) date, so I did.
I'm afraid that information is frankly misleading.
My shortcuts option 23 gives an easy way of reverting, and stil works - and takes no more than about 30 seconds in Firefox.