"They are part of the seat, built in, as they are on a coach, they are coach seats. Probably safer than the ones land rover do, and they don't connect to the chassis??"
Yes they do. And in a bus you can have the seat belts attached to the seat structure, if the seat structure is bolted to the vehicles structure(chassis) or rails bolted to the vehicles structure(chassis)
And the angle of the shoulder straps on the front seats will compress your spine in a frontal impact.