There are 5 links tagged.
Added: 24/03/10 Tags: postcode
http://www.hm2k.com/posts/how-to-search-by-nearest-uk-postcode-in-php
http://luckylarry.co.uk/2009/07/google-maps-api-part-1-accurate-geocoding-for-uk-postcodes/
http://aciddrop.com/2007/12/17/quick-easy-and-free-nearest-store-postcodezip-finder/