I am assuming ‘British’ refers to Dinky rather than the vehicle. Dinky 949 the Wayne School Bus has the side rubbing rails; these all terminate before the rear corners. In the attached photo which includes a picture of a real Wayne Transit school bus it can be seen that the upper two runs extend around the rear corners. In the photo too is a model of a Thomas bodied school bus with wrap around rear rails. 282 Leyland Royal Tiger Duple Roadmaster Coach also came in yellow with red added in the style of a school bus - for US marketing perhaps? As in Journal 86 July 22, the reuse of the 949 casting as the Continental Tours coach is noted; besides the unsuitability of the door positioning (and possibly the stop/start engine and gearing) the reuse of the interior modelling is shortsighted. Period school buses often had wooden seats and spacing suitable for children and (speaking from experience) very uncomfortable for adults; a lack of a toilet cubicle too would make those continental tours somewhat unappealing.
It is true that the side rails usually extended around the back of the bus, as the attached picture shows. But whether this was an inaccuracy in the Dinky (maybe for technical reasons?) or merely reflected variation in the coachwork used by Wayne Works, I am not sure.
The second picture I have attached shows that Wayne did advertise a "luxury cruiser" version of its bus, which certainly would have featured different seating, gearing, and maybe a toilet. Whether they actually sold any, I cannot say.
The U.S. school buses of this period actually had metal seats with thin padding. As is still usually the case even today, they did not have seat belts.
I think it's only coincidental that the Wayne luxury coach is a shade of blue like the Dinky. The Continental Tours model was merely a rather cynical (but attractive!) invention by Meccano Ltd.