I have been researching London buses in WWI for many years and have written a book on it. I live in Colchester just a short way from you. I have seen your Daimler lorry at the Chalk Valley show. I would love to come and see it. I have drawings of the chassis and many photos of the Daimlers in service and the markings used. The Daimler buses were used by the Royal Marine Transport Company at Antwerp and then they were transferred to the army as the 16th Auxiliary Omnibus Company which used the Britannia penny badge which is incorrectly used in the Airfix kit of the B-type. Further detail in my book Ole Bill - London buses in the First World War. I gave a copy to Colchester Library so it should be easy to get it to read.
The London Transport Museum has restored a B-type bus and has some of the moquette material to cover the lower deck seats. They would also have templates for the upper deck seats? Try writing to Chris Nix at the LTM.