How do you connect towbar wiring on a Nissan Serena MPV?

I have fitted a towbar to me Nissan Serena (import) MPV and am now doing the wiring for the electrics.

I cannot see how to get the wiring into the vehicle. The rear valance seems to be totally enclosed.

There are wires coming out of the valance for a foglight bu tI cannot see where they go. You dont seem to be able to access the rear from inside and when you remove the rear lights you dont seem to be able to get down to the valance either.

Does anyone know where to run the wiring - both for the trailer lights and for the caravan socket...