I’m on the fence. Ouch.
But, regarding the on/off the licence thing it seems to me to be an admin issue. The O Licence covers authority to use x amount of vehicles/trailers from your operating centre as well as financial standing and good repute etc.
Now, if you’re operating more than permitted from the O centre you’re in breach. However, if you’re traction only and collect/return your trailer from the customers location; and if the customer is responsible for the upkeep of the trailer (financial standing); then is it a breach in anything other than a technicality (good repute)?
Still on the fence.