Richard,
Did you ever find a Commer spare parts list? If still needed, check the Commer Q2 tread here:
http://www.mapleleafup.net/forums/sh...154#post262154
The IWM also has a 1944 Commer Q4 spare parts list - see
https://www.iwm.org.uk/collections/i...ect/1500086879 - and maintenance manual - see
https://www.iwm.org.uk/collections/i...ect/1500086880
Hanno