Zend certified PHP/Magento developer

Autofill Postcode/Zip Field in Estimate Shipping and VAT

As part of a project I am working on, I need to set the customers postcode using localStorage anywhere on the site to allow other postcode functionality to occur.

Part of this is to also autofill the Estimate Shipping and VAT Postcode field so rates are shown straight away. By default magento populates if the customer is logged in so this is fine.

Can anyone point me in the correct direction to get the Postcode Field auto populated based on a session variable or localStorage variable?