Not having a motorhome I can't be quite sure about this, but my belief is that a towed car must be on a trailer with all four (car) wheels off the road and not on an A frame.
Certainly so people on the same campsite in Spain earlier this year had been fined 200 euro for using an A frame and the lady had to then drive the car and follow the motor home over considerable distances.
Suggest you check with Caravan Club or C&CC.