Based on the documentation of the companies house UK and postcode lookup on my instance of Contract Express, I need to request for an API key to add to the datakey value of app web.config
Please send the API key to my email - jamestai@paulhastings.com
Sorry but we do not support ‘Contract Express’ nor know what it is. The only API keys that you need for our API services can be obtained from our administrative interface https://developer.company-information.service.gov.uk/ once you have registered and signed in.