Re: Wear the mask
"Fact is, they are are extremely useful and successful at both reducing the the potential for person to transmit it, and for somebody to actually breath it in."
Two different things with two different requirements. Preventing breathing it in requires an expensive mask with a proper filter system to trap aerosols and HMG quite rightly doesn't want people stacking these up alongside their mountain of toilet rolls, paste, flour etc. when the front-line needs all they've got.
Preventing transmission of a disease people have needs something to catch larger droplets. It's a lower spec providing you don't take it off to cough but if you're coughing best to stay at home and do a proper job of avoiding transmitting the disease.