When Caldbeck switched over to digital the signal strength was so high I had to fit attenuators to all equipment. Six months ago I had to remove them. I now often get lack of signal check antenna.
BBC 1 strength is about 70 -73% but ITV4 is down to 40% ish.
Other than that you should talk to your neighbours to see if they have the same reception problems. Then contact whoever is responsible for your communal aerial system.
Caldbeck is the correct transmitter for our area CA14. The only other person on the same ariel mainly uses sky, like the wife, I’m relegated to the spare room with free-view. But the wife admitted there was a problem as she was recording 2 things on sky and had to use the tv tuner. She was amazed that it dare happen to her.
I think I best contact our housing group to get it checked.