Citing a useful source
The code for calculating the distance between points that I have posted in C# was based upon the work published at: http://www.movable-type.co.uk/scripts/latlong.html
Anyone interested in this should also look for a downloadable list of UK postal OUT codes which is freely available (If I find the link then I will include it here).
All these things can be put together with something like Google Maps API to display routes, POIs and locations.
