This is unusual and I would suspect that the UKVI have made an error. For certain types of application (eg/ settlement applications made from USA) all documents need to be sent by post to Sheffield after the applicant has provided biometrics. However for most other applications worldwide, you submit the documents when you visit the Visa Application Centre. Therefore if you submitted everything to TLS you should not be required to take any further action. I hope you do not have to wait much longer for a decision, please do keep us updated.