The X5 also has two ex Cambridge Park and Ride vehicles 10803 and 10804.About 10% which is really quite a bit.
As an aside, and not aimed at you, but there does appear to be an enthusiast's hierachy
Solo or other mini... It really must be single deck
Single deck... It really must be a heavyweight single deck
Still a single deck... It really must be a double decker
It's a double decker... It really must be a dual doored double decker (cue discussion about bus company conservatism, dwell times, ticketing, how much better everything is on the continent for the 289th time)
As it is, the Busway has provided a steady stream of vehicles to be cascaded to the wider Stagecoach East fleet. However, and I noted this on my excursion to the area in July, the Stagecoach East fleet is looking a bit peachy now - no real relics to think of but definitely looking a bit middle-aged. Don't know what the age stipulations are on the Busway (are there any?) but 09 plate Eclipses are showing their age, and Peterborough seemed to have a lot of stuff from 2010-2012... did they lose newer deckers for the X5 or am I misremembering?
Peterborough now has a big chunk of the double decker fleet that was new to Cambridge in 2010, less than a third of which are still in Cambridge, and quite a few have also gone to Bedford. These have mostly been replaced in Cambridge by ex busway double deckers, some of which date back to 2009 when the busway was new. The ex London double deckers, that arrived in Cambridge just before COVID, have disappeared recently, bustimes says they are now in Canterbury.
The small Cambridge single deck fleet is still dominated by the vehicles that were new in 2013, supplemented by even older vehicles, including oddity 27522 registered in 2006.