VWL119 wrote:
On the other hand if they convert AV118 they are getting something considerably newer, something more economical and less polluting to the Environment and most importantly it is low floor.

Not nessisarily , many operators are trying to have Euro 6 emmissions standards postponed as Euro 5 engines consume more fuel and produce more carbon than Euro 1 or earlier engines due to the increased weight (for example a 9 ton Routemaster produces less carbon than a 17 ton Wrightbus/Volvo B9TL), so newer is not really cleaner.
As far as I know the Leyland engine and gearbox in the Olympian is really only an updated version of whats in the Atlantean , the Volvo Olympian is a different kettle of fish however.