You see them on shopping carts etc, you type in your postcode and it gives you a list of house numbers, then the user selects the house number from the list... Is this just done with a database or is there anyway to do this using google maps or another api?
this is for the UK
I have implemented this before for clients. The only reliable way i found was to use a comercial API. the cheapest and most reliable i found to be "postcodeAnywhere"