We have contacted HMRC to clarify the following procedure:

“If the goods I am selling are VAT exempt, I should be able to charge 0% VAT on the postage of that item as well.“

HMRC has assured us that, although it is possible to do so under a very niche set of circumstances, this is not classed as standard business practice when selling goods over the internet. Although you are obliged to send the item to the customer, this does not count as a "Contractual Agreement". 

Because of the vague interpretation of this method, and the complexities of implementing such a constrained practice into our system, we have decided to forgo the development of such a feature until a point when HMRC can clearly define under what circumstances this method can be applied, and the necessary tools and resources to manage this process.

In the rare case when Shipping Tax should not be applied, you can use a free of charge macro created by our team to assist you in automatically changing these required orders.  

Please see here for full details and instructions for setting up the macro.