1. Get the UK postcode web service.
2. Create VS project, Add Service Reference of url "http://ws1.postcodesoftware.co.uk/lookup.asmx".
3. Create static class of your own code.
4. Build solution, a .dll of postcode will be available.
5. Create New Dynamics AX project in VS with Class.
6. Add the Reference of postcode .dll to the project.
7. Create extension for LogisticsAddressSetup form.
8. Copy ZIpcode control's event onModified and past on the class.
9. write code ur logic.Provide Postcode in Zip/ postal code field the rest highlighted fields will populate automatically.