(30 Nov 2014, 9:57 am)Tom wrote I will - it also seems to happen on Sundays, I have seen MAX vehicles on the X21/X22 on Sundays. 

I know it would have cost more but I think Arriva could have done this instead of what they did do:
17 New E400's for X21/X22
7514-6 Refurbished for X15 along with the two Omnicities 
7517-21 Refurbished for X14, with one as a general spare
5 New E400's for X18 (As they have done)

Leaving 7501-9 and 7511-3 for other services, to improve reliability on the more "premium" ones...