Here (in Wales) face coverings are mandatory when travelling on public transport, but only then.

Apparently this is based on WHO advice, as per the Welsh Government website: Here

At the present time, the widespread use of masks by healthy people in the community is not supported by high quality scientific evidence. Social distancing and hygiene measures remain the most effective measures for reducing transmission of COVID-19.

The WHO is recommending, though, that as part of the wider range of measures to prevent transmission, three-layer face coverings should be encouraged in situations where social distancing and hygiene measures are difficult to maintain.

There is evidence to suggest that the wearing of face coverings gives people a false sense of security which makes them less careful about social distancing and handwashing. We know that these measures are the most effective way to reduce transmission of the virus, and don’t want to do anything that might lead to a reduction of those measures being observed.