Hi There,
We've been working on an app that might solve your problem.
The app is called Better Shipping and is currently in beta. It can be found here http://apps.shopify.com/better-shipping in the Shopify App Store.
Better Shipping allows you to set the delivery rate on a zip/post code basis. It also allows you to limit deliveries to certain areas only and set delivery rates for individual products.
Please feel free to contact us if you have any questions - support@atomyard.com.