Initial idea was to have one cache hidden, and give co-ords and questions in a number (4/5) of the villages on the route. Answering the questions would give co-ords for location of cache.
This way the cache could be completed in one day by driving the route (something a number of fans do anyway), or over any time period and by visitng the locations by any route.
I've also considered making some of the clues solveable using Google street view. This way the route could be brought down to 50 miles.
This is an area I visit often anyway, and I was surprised that there weren't any caches already in the location. Maybe motorsport/geocaching isn't a common mix of interests?