Hilary asked me whether I knew of the Hayhill Army Camp. I mention it here as this is of direct interest in this forum.
Basically, I assume Hayhill must have been the official name for the Canadian Army camp near the Slough Trading Estate established sometime in 1940. As you all know the second Canadian Mechanization Dept was set up in the former Citroen Cars Limited works on the Slough Trading Estate and some RCAOC [Detachment 2] personnel were assigned to the CMD to assemble Canadian Fords and then Jeeps from autumn 1940 onwards.
Note the location of the camp to the CMD in the top right corner. There was also a British RAOC depot/vehicle park that had hundreds of vehicles stored therein in 1940-41.