This application is the public-facing system where applicants can respond to validation requests sent by planners through BOPS. The only way this url is shared is via an email that the applicant receives after a validation request has been sent from BOPS. The application url has one resource: validation_requests, which contains the planning application id and a unique change_access_id (for security purposes) as query parameters. The base url will not resolve anywhere without these parameters.
https://planningapplications.buckinghamshire.gov.uk/
https://planningapplications.buckinghamshire.gov.uk/validation_requests?planning_application_id=XX&change_access_id=XXXXXXX
You can find the public repository for BOPS Applicants at https://github.com/unboxed/bops-applicants