I've now discovered how to make my own maps in the JNX format which are much, much better than the Garmin ones. I have configured the zoom levels to suit my requirements, the maps are clearer and seem to load quicker. The only down side is the size, the Lake District map is 2.44GB as against 396MB for the Garmin Discoverer but this does contain both 1:50K and 1:25K mapping. I can have any area I like, all for just a little bit of my time. For anyone interested I use the below software to achieve this.

Mobile Atlas Creator (use Multimap OS maps and save as Oziexplorer format)
[Only registered and activated users can see links. ]

MPAC2MAPC
[Only registered and activated users can see links. ]

You do need to use hacked firmware but I have not found any adverse effects to this. The hacked firmware is linked in the initial post of this thread.