Wow Brian, I'm surprized that you drove through a council estate. Considering that cars no longer have tax discs , someone must have told you. Or perhaps you secretly go round checking up on cars in council estates , looking them up on your computer and then report any that are not taxed and / or insured.
Why would you put a sticker on a car that was being 'lifted' - to remind the DVLA why they lifted it ?
I'm sure we are all grateful that the streets have been made a safer place.