You seem to have an untraceable water leak in the boot of your 2007 Skoda octavia any answers?

If you have a rear window wiper, the connection to the wiper feed may have detached through the pipe freezing.

In the estate version this may be accessed by removing the top lining panel above the rear window. This has to be eased off and care must be taken not to break the four corner locating pins.

Hope this helps