After doing some research on this, this can get extremely complicated. I've seen some code that use COS, SIN and other types of math formulas I haven't done since high school..

Anyways, for you UK folks, I found this website if any of you are interested.

http://www.milldo.com/en16_uk_post_codes_database.htm

And here is the formula that seems to be the most accurate..

http://en.wikipedia.org/wiki/Haversine_formula


It's all just a bit too much for my current skillsets right now...