yes its behind the boot trim, can be found by following the harness back, from the rear light
Ok thanks Ivan for the nautical explanation

Eeehm....just had a look again....if there was an access hatch or something ok, but the boot trim is one piece from floor to celing and
from back door to the boot lid. Have to dismantle half the bloody rear end to get at the cables

Have got one working trailer board so me thinks the missus can drive WJ with working X-mas tree following close behind me in the KJ.
...don't have to go that far.