Having spent time living in both cities and near the country I've seen a variety of night skies ranging from a light grey haze that I could read a book under to darkness so intense I couldn't see my feet (it was cloudy unfortunately...). For some reason I can't see stars dimmer than 5.8 or so with the naked eye regardless of how dark it is.

Luckily where I am (Somerset) I am not too far away from some very dark skies and being a bit of a sad git, uh, geek scientifically minded person I wanted to have a way to work out which of the two or three sites I use are the darkest. Using just my eyes appeared not to work in that I could never quite see the dimmest star in the dipper of Ursa Minor even at very dark sites. The darker a site appeared to be on paper the lighter it looked to me as my peripheral vision was picking up stars that I couldn't see and making me think it was haze/light pollution.

Using the Bortle scale (http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y) helped a little although the Naked Eye limiting magnitudes the scale used were in the order of a magnitude out for my eyes. So... I bought a Sky Quality Meter. This pretty quickly showed that what on paper were the darkest sites were indeed darker with the best reading being a 21.67 in north Devon. (Kelling Heath this April scored 21.66, virtually identical). Since then I've seen that some sites in the US literally hundreds of miles away from light domes get similar readings or even slightly worse. This could be an issue of the calibration of my SQM of course and has now called into question the point in using the SQM.

So until I find someone else with an SQM that I can calibrate against mine I'll make do with the approach demonstrated by an SGL Admin at Kelling Heath where he looked up towards Polaris and took a long few seconds to see it amongst all the other stars... as he said; if it takes a while to find Polaris it must be dark!