Plot hole: Why on earth do they drive the Minis up the ramps into the bus while it is moving? They are on a long, straight, relatively quiet stretch of road, but there are cars and buildings about. That ramp is going to make a noise like the sky coming down (we see sparks as it scrapes on the road) and they put on a display anyone would be, frankly, amazed to see. Don't they think one single person would call the police? Don't they think that reports of three brightly coloured Minis will be connected with the recent robbery? They cannot possibly think they have to load the Minis on the run in order to elude the police; they have lost the police cars and are no longer being pursued. Why not just park the bus on the hard shoulder and drive the Minis sedately up that ramp? An unusual sight, maybe, but nowhere near as clumsy, obvious and attention-getting as the way they do it. They are asking to be pulled over and arrested.
Plot hole: When the minis drive onto the roof of the leisure centre they are trapped - all the police had to do was block the entry/exit ramp.