Shipping to 14 set locations (not to other locations)

[LeeseRogers-Bay]

Hi there, 

I have set up a gift store for our staff's internal use only - to provide gifts for their clients.  We only want to ship their purchase to our 14 set office locations (ie, we don't want to ship to home addresses etc, just our 14 offices).

Shipping prices for these 14 office addresses fall under four different "zone rates" - some are closer to our head office where orders are to be shipped from, some are further away etc.  I have the rates sorted, I just need to know how to have just 14 locations displaying as shipping options at check out (I also need pick up to still show - as it does now).  

Side note 1:  The offices all have different post codes.  
Side note 2:  The store is password protected as it is only for internal use (ie, not available to anyone outside of our organisation).
Side note 3:  I would really like the office locations to show in a list under the delivery method heading during check out.  So instead of our staff putting in their address, I would like the office delivery address list to populate at checkout.

Any help / advice greatly appreciated.