DanP
I hope I can get this setup explained correctly but you should get the idea.
First thing BACKUP, BACKUP, backup, did I mention to backup your site and database :D
I am running the latest ZenCart 1.3.8a
I have installed Vat-Mod from here:
http://www.zen-cart.com/forum/showpost.php?p=509374
I then downloaded UKCounties2, see below, opened it with a plan text editor and added the Channel Islands I wanted to use to the list, the syntax is easy to follow and you should make any other changes you want to the list, then uploaded it to ZenCart via pasting it into the "Install SQL Patches" in the admin area do not use the file upload, use the paste in window.
http://www.zen-cart.com/forum/showpost.php?p=249449
Now you will need to add a new "Zone Definition" I called mine:
Zone Name: Channel Islands
Description: Channel Islands no VAT
Next add a new "Tax Rates" for each Channel Island you want to not charge VAT for.
Tax Class Title: Taxable Goods
Zone: Channel Islands
Tax Rate (%): -17.5000 (Note the "-")
Description: Channel Island NAME
Priority: 1
And last but not least set the Config> Customer Details> State - Always display as pulldown? to true.
I think that's it.
If you would like to test I will PM you the URL to my test site to try different UK address I currently only have "Jersey" setup to not charge VAT.
Dave G