I personally think there is much to be said for keeping the base map on the GPS fairly simple and straightforward with just the basic route, airfields waypoints, VRPs, obstacles and airspace boundaries. I find the actual CAA chart representations too potentially confusing and with too much unecessary information for use in flight on the GPS screen, and prefer to use the chart for preliminary planning and then the GPS for the purely navigational function rather than as an information source in its own right.