First off, I'd like to note that Ordnance Survey maps sound remarkably similar to USGS topological maps for the US, the basis for maps you can load onto hand-held GPS devices often used for back-country or wilderness travel. However, you still need to be able to read such maps to get around. The ones in cars orient themselves, and read to you; some in Japan even show three dimensional views of city buildings and streets, overlaid with bright arrow paths indicating which lane to be in and where to turn!
Next, I'd like to marvel at a resonance I'm picking up between what Nick says about handwriting and mapping styles (17 March 2010, 05:55 PM), and what Emma reminds us with regard to boilerplate-style application of learning styles (18 March 2010, 08:14 AM) to accommodate a variety of, and variations in, learners' preferences.
As a case in point, a colleague sent me back two maps that I'd prepared on related perspectives of a joint project, at different times, with the same mapping tools (IHMC Cmaps), and suggested that visible differences in the mapping styles deserved further exploration.