That looks like a useful platform for folks in the UK. I'd be interested to understand more about their methodology. I live in Austria, so tend to use the IAQCN station data (which is not always validated) aqicn.org/map/world/ . The UBA stations are more reliable, but coverage is sparse in places.

Air Pollution in World: Real-time Air Quality Index Visual Map

How polluted is the air today? Check out the real-time air pollution map, for more than 100 countries.

That's a useful resource too, thanks. I've no idea how addresspollution did their work, assumed access to air quality monitoring stations but how the algorithm apples that to addresses is an unknown, to me at least.