I've been trying a tomtom one for my uncle. The first time I used it every thing worked fine but today theres no real time map just a dark blue screen with an arrow on it and showing the road your on and the next turning you need to make . I can't find any setting to change it back to the map.

Sounds like you've somehow set the "hide map above x mph" to a silly level or turned it off completely.

Tap any part of the "map" display to show the menu. The tap "Change Preferences". Tap "Safety Preferences". Ignore the list of tick options and tap "Done", keep tapping "Done" till you get the "Turn Off Map Display" setting. Select "Above Certain Speed" or "Never" (I suspect it's set to "Always").

If you select "Above Certain Speed" and tap done you get the option to set the speed at which the map changes to the arrow mode. The lowest setting is 20MPH which could hide it in most driving - M25 rush hour excepted obviously