I'm really sorry that your delivery was returned. They are signed for and Yodel should have left a calling card if they attempted to delivery it. I believe they try a few times before it is finally returned to us.
You can call our pre-installation team on 0800 052 1734 and they will be able to send out another Quick Start kit for you. If you think you are not going to be available to sign for the kit you can chose to have it sent via Click and Collect.