Does it do full UK postcodes or just partials?
How do you get the maps updated?
Does it carry speed camera data and how is it updated?
Does it have PoI's and how do they get updated?
Does it speak English with a clear British or US accent?
Finally - and most importantly - how do you get it fixed under warranty?
From reading reviews from various sales sites the overwhelming view is that they are not good.
Comments include unable to update maps, difficult to use, does not take account of vehicle size even though size entered, handbook useless.
I am on my second Pro Drive Europe sat nav. You can put the length, height and width weight and number of axles. It has over 30,000 campsites loaded. I paid £79.99 for my latest one. I only got rid of the first one as I couldn't be bothered to update it. I had it for 5 years so it only cost me about £17 a year. The only time it took me the wrong way was when I put the wrong destination in I will most probably get a new one in another 3 years if this one needs updating as I can't be bothered to.