I think the biggest concern with regard to wearing masks, is that it would take them away from people that genuinely need them.
Already, most dental practices, which are allowed to stay open for emergency treatment (just not for checkups, teeth whitening, etc), are having to remain closed because of the lack of masks. I know someone who is in a significant amount of pain because of something that could be resolved by an emergency dentist, and whom is a key worker, but is unable to get an appointment at their usual dentist, or anywhere else in their city.
Indeed, PPE is already in huge demand and short supply. The last thing we need is mass panic buying of it, and we simply don't have the resources to make them easily available to the general public. And even if we did, there is still no real consensus on their effectiveness on preventing infection for the public at large. However, for those with mild symptoms....
If you are showing symptoms you must not leave your home for anything other than medical attention which NHS111 or your GP has advised.
Exercise must be taken within your home and food must be delivered.
Might there be a case here for an East Asia style of culture of wearing masks if you have a cold or mild flu symptoms in the longer term? Obviously if the symptoms are more serious staying at home & contacting the NHS for advice is prudent, but we live in a part of the world plagued with viruses that cause similar effects, so we need to be able to mitigate for that. The only possible downside might be that such a change of culture after the fear that this situation has caused could lead to animosity towards people following these kind of protocols.
I think there is quite a lot of potential in the anonymised mobile apps, using GPS and Bluetooth together (but not storing the location, just using it to "weed out" false matches) myself. It doesn't require full compliance, it just requires enough compliance. (I feel like I'm talking about the proposals I made a while ago for e-ticketing which were rubbished by many on the Forum because they didn't provide a perfect way of preventing fare evasion - turns out they were "good enough" as they pretty much came true).
I think compliance will be high if Google and Apple build it into their OS and make it the default (i.e. active opt-out), which sounds likely.
Thinking more about these kinds of solutions, they really could only ever be used as an advisory system, i.e. "You may have come in contact with someone who has subsequently reported possible symptoms. Please seek medical advice if you develop similar in the next 7-14 days", or something along those lines. I honestly don't know that it would be reliable enough to be any more than that, mobile GPS whilst often very accurate can still have wobbles, especially if indoors, and Bluetooth is really only going to tell you that someone was within its range (up to about 10m IIRC) but not necessarily within risk range, (1-2m).
Personally I wouldn't be adverse to using it myself, I do use GPS routinely with my Android devices to feed useful information, but I wouldn't expect it to be entirely accurate.
I don't see how the hospitality industry can ever fully re-open whilst this virus remains so dangerous. If pubs re-open, there will have to be strict capacity limits in force, and noise limits as well. You can't have people in pubs shouting into each others ears to talk because loud music is playing.
It actually wouldn't half as difficult as you might imagine. My local pub directly prior to closing had changed it's seating arrangements to allow for more distancing, & had upped it's cleaning arrangements (i.e. a full clean of tables as soon as vacated as with restaurants). So add in at-table service, maybe using a mobile app wherever possible to reduce staff movements, along with capacity reduction (e.g. no standing at the bar)
As for bars, nightclubs and concert venues, I don't see how those can re-open at all in a Covid-19 world. Nightclubs and most concerts are all about being packed in with lots of sweaty people with very loud music. A perfect 'super spreading' environment.
In the words of the Danish Prime Minister, "We cannot lockdown forever". And we can't, sooner or later people will congregate.