For my job I travel to different shops within a town throughout the
day. I program them into a Sat Nav system using the postcodes. But it
will not sort them into an order, i.e. it will not take me the
shortest way around them, and I may go from one side of town to the
other and then back again. I am wanting some software that will sort
the post codes so i can enter them into my Sat Nav system in the best
order, so as to find the quickest way around.

I have not tried it yet, but the AAA trip planner is supposed to be
able to handle multiple destinations.  You might want to give that a
try.

Thanks for that but im wanting it for UK routes.