(16 Mar 2020, 6:17 pm)peter wrote My calculations left me with 4 spares,

40/41 PVR 5 - New 41 PVR 4 = 1 spare vehicle
42/42a PVR 8 - New 42/42A PVR 5 = 3 spare vehicles

If at all possible, could you point me in the right direction as to where I've gone wrong?

You're right, with one added back in for the transfer of the Byker ASDA service from Riverside to Percy Main (which will operate service 19 in the peaks). The bus which currently operates the Byker ASDA bus will remain at Riverside to operate the scholars service attached to it currently.