Superb Dave! Thanks for posting these additional Serials.
At the very beginning of IWM Film
A70 135-3 we can see:
1. A truck with Serial '1318d' ('d' meaning "with diagonal bar from top left to right bottom"):
2. A lorry with Landing Stage component, Serial '1302d', vehicule number K33:
This is a Canadian unit, viz the Census Number starting with 'CL':
3. Another Landing Stage component lorry (K18) of the same unit:
4. An FBE truck, Serial '1317d', meaning 106 Br Coy RASC:
Sadly, the sequence stops there
Close enough to, but not quite, '1303' (presumably with the same white bar and formation sign) for 86 Cdn Br Coy RCASC as you found
Michel