You can use this UK postcode search to find a postcode for a given address. At present it contains most of the UK's postcodes. All postcode searches are logged and any valid UK postcodes that do not return at least one address will be inputted into the database.
I make no claim that the information in it is up to date or accurate. This is not intended to copy or compete with any existing web sites. I cannot and will not be held responsibly for the use or accuracy of any information given.