Ok, I have been under and checked them. There is a "R" on the right hand one and a "L" on the Left hand one so I presume that they are right. The handbrake cable leavers on each do poke towards the front of the trailer. All parts inside appear to be installed properly.
I will try and source a DC clip on amp meter and check that too. Does that just clip on to the magnet? (pardon my ignorance);-)