Hi,
To check the level of light pollution at a specific location in the British Isles (or overseas) I use
https://www.lightpollutionmap.info/
I find that its SQM readings and Bortle Scale estimates are in good agreement with my own obtained on my travels.
Additionally, use
https://lighttrends.lightpollutionmap.info/
to click on a location and generate a plot of the trend in light level.
Clear skies,
Alex.