the problem i have with my garmin is that the night vision screen comes on during the day and as there is no manual setting to adjust it there is nothing you can do,however when you remove it from the power the day screen comes on but when you plug it back in it goes back to the dark screen. i thougt the time setting maybe wrong but it isn't it automatically does it itself.Do ineed to take it back to Hallfords?
I have the same sat nav, There is asetting for day and night screen. Go to tools then settings, Then to display, when there you will see colour mode it will give you 3 options when you go into it, Day, Night and auto.