Adding a postcode "exclusion list" to manual shipping

I have a client who is offering free shipping via the manual shipping plugin but with a list of excluded postcodes (remote mining areas etc). Because the excluded postcodes are widely dispersed, activating separate shipping plugins for each allowed range of postcodes will result in dozens of instants. What I would like to explore is adding an array of excluded postcodes to override the included range. EG. Postcode minimum and maximum may be 2000 to 2800, But the array of excluded postcodes might include 2457, 2522, 2524, 2677 etc.
If the shipping address includes an excluded postcode the shipping option should not display.
How would I go about modifying the Manul Shipping pugin (ie. a copy) to do this?

The direct link can be found here...
brainforge.co.uk/shop/paid-downloads/hik...hopshipping_bfmanual

Fantastic. Its almost as if they read my requirements list.