There latest fleet list:
Active fleetlist as below:

YJ13HJA OPTARE SOLO SR
YJ61MMX OPTARE SOLO
MX61BBU WRIGHTBUS STREETLITE DF
YJ11OJL OPTARE SOLO SR
MX60BXD WRIGHTBUS STREETLITE DF
CN07KZR OPTARE SOLO
YJ06FZP OPTARE SOLO
YN06RVY MERCEDES VARIO BEAVER 2
AU54JRV MERCEDES VARIO BEAVER 2
YG52DFY OPTARE SOLO

RJZ9829 DAF BOVA FUTURA
NC06UAZ FORD TRANSIT
CV61ZHF FORD TRANSIT

Thanks to Peter Hogg for the confirmation, there Optare Excel has been withdrawn but remains in the depot.