Getting conveyed to /from the a/c with all of the classes happens all of the time wherever you are.
Have you ever been outside LGW?
Because what you posted is not correct.
And no, we are not missing the point, this thread is about how to irritate premium pax and mixing the classes on crowded busses (in fact busses period) are a pretty good way to do this.
When premium pax pay 000s for a ticket, we expect to travel in comfort and without stress.
Capetonian summed it up a few posts back, so I won't repeat.