Tracking an application. Our Mortgage Application Tracking System (MATS) keeps you up to date with the progress of your client’s application up to the point of completion. It is fully integrated into Introducer Internet giving you a simple summary of all your cases. You can also view copies of your uploaded documents and notes. Santander UK plc. Registered Office: 2 Triton Square, Regent's Place, London, NW1 3AN, United Kingdom. Registered Number 2294747. Registered in England and Wales. www.santander.co.uk. Telephone 0800 389 7000. Calls may be recorded or monitored. If you already have a Santander mortgage but want to change your deal, applying online may be an option for you if: You're happy to choose your new mortgage deal without the protection of advice (this is also known as Execution Only).