A new timetable for the National Express service 727 commenced on 29 November 2021 featuring two trips from Great Yarmouth to Heathrow (worked by Ambassador Travel) and two trips from Norwich (UEA) to Heathrow. There is also one trip from Norwich (UEA) to Stansted (The UEA services are all worked by National Express in house).
The Great Yarmouth-Norwich-London services 490/491/492 remain unchanged and it would appear that Ambassador Travel are still working these.
The above changes would perhaps explain why Volvo B8R BK15 AJU was added as an extra vehicle to the Ambassador fleet of late from West Midlands Travel.
I am grateful to David for the information and photo