Thanks Igor.
Geo, forgive me please; you asked a sensible question that I failed to answer right away. The silver boxes represent various control valve boxes which, according to my manual for the Mk. 40, which is a late Fighter Bomber, control hydraulics and pneumatics from the engine pumps to the cockpit controls and back out to users like the bomb bay actuators, flaps, tail wheel retraction, etc. The holes you see in Bulkhead No 2, pictured above, provide access for the tubes to and from the various cockpit controls. The pipe layout on this bulkhead on the FB versions is different than that of the bomber versions and, unfortunately, I don't have a manual for the B Marks and the B Mk 35 plans I have don't cover the hydraulics.
The boxes are made of bits of plastic card and rod and were glued using thick CA directly to the painted bulkhead. Not very strong, but then it doesn't need to be.
At present, I'm trying to figure out what the thick pipe is going from the top of the bulkhead, down, and over to the left in the above photo. I don't know where it heads after turning at the port fuselage wall so need to keep looking for references in this area.
Thanks for your interest.