IO,
Agree with you that kegally you may not be responsible, however, I am sure that if you signed someone off for the club you instructed for and he then promptly rented the complex and stuffed it into the deck doing £££s worth of damage you WOULD be responsible in your employers eyes and looking for a new job!
The club I use wants 5 hours dual to rent the complex and either 25 hours dual multi with one of their instructors or 50 hours TT multi for solo hire.
Julian.