The point is that British operators have no choice but to go for the cheapest option. Continental operators could also buy British buses if they wanted but they actively choose to pay more for something different. So if ADL vehicles (for example) were both better and cheaper it would be a no brainer to buy those instead of paying through the nose for, say, Mercedes or MAN. When tendering started in the Netherlands, Arriva did use some Dennis vehicles as there was a natural curiosity to see if those vehicles would work given the then British ownership, but as far as I know there aren't any ADL vehicles there now. A few Optare Solos (or Versas?) are in operation in the Netherlands though.
Obviously too, continental operators could opt for denser seating if they wanted. Cost isn't the issue. But denser seating with fewer doors has a negative impact on dwell times.
That's not necessarily correct.
There's a number of operators who have elected to go with European designs. Go Ahead and First have Citaros. Arriva, First and Go Ahead have Omnicities. That said, perhaps there is an element of supporting local native suppliers - certainly a factor in France - on both jingoistic terms but also because of the quality and availability of support. One of the reasons why Iveco nor Renault could crack the UK market was because of the lack of servicing back up. Much easier to get replacement parts etc for UK produced fleet.
Also, my point is that the idea of "quality" is rather subjective. Having enjoyed operations in the Netherlands, Iceland, Spain and Italy, my experience has been that they have gone for the bog standard, multi door, citybus with minimal and highly uncomfortable seating irrespective of whether it is a feeder into a rail/metro/tram system or a longer duration service.
My profile avatar shows such an operation. An urban 3 door citybus in Valencia that I would typically spend the journey standing for 20+ minutes as the Metro doesn't serve that part of the city. In the unlikely event of getting a seat, it would be a moulded plastic example (not cushion). In that respect, I would much have preferred a standard e200mmc!
Also, we hear people on message boards referring to double glazing on vehicles. However, I never hear it on buses on which I'm travelling (heating, seat comfort yes but never double glazing) and we don't seem to require it in cars (the mortal enemy of the bus).
There have, of course, been plenty of examples of exporting to the colonial commoners. My most surprising encounter was in Squamish in British Colombia with Plaxton Pointer bodied Dennis Darts working within the Rockies!