2 options put resistors in the connectors to fool the car into thinking the seat belts are connected, Or using the Renault clip now I might not be 100% here but I believe the configuration can be altered so the car thinks no rear seatbelts are fitted as if it was a van but the resistors would be the cheapest option.
Now before you ask I don't know what resistor sizes that are needed, and the Renault clip of mine I have used to diagnose an airbag light problem as the system can tell you the current resistance value in each circuit which I used mine to work out which airbag was causing it and cleaned the connector up which fixed it. I would say dealers will not disable airbag configs for legal reasons especially if the car is used on the road. Your profile says Sligo but you posted stuff to Cornwall KTec racing near you should be able to help I think it's 3.3ohms but careful where you put them you don't want to trigger an air bag by accident especially when your in front of it.