In reply to Martin McKenna - Rockfax:
Both WalkHighlands and WalkLakes have 25k OS mapping if you register for free. Contours are pretty vital for navigation.
Instead of looking at Ben Nevis try a less featured area!
Walkhighlands has the edge on the interface (though not perfect by any means). Your overview map, similar to the UKC crags one, is not the greatest way in to the fine detail.
I do admire what you are doing though, but the 25k map is not much good.