Removing the seat will not necessarily cause the airbag light to stay on, but if it does this would be an MoT failure. There would also be the issue with the seatbelt pre-tensioner for the passenger seat, which could cause further problems if disabled. Resetting the airbag light would only be a temporary fix and would likely illuminate again when the car is switched on.

If you need to sleep regularly in your car, we would suggest folding the rear seats down and using the boot space and rear seat area. It would not be spacious, but a decent quality roll-up mattress and sleeping bag would be a less expensive and troublesome alternative.