To my knowledge the green leaves ARE toxic, at least to some degree, but they don't eat them. The dead weathered leaves on the ground are NOT toxic. I know this because it is common practice among exotic roach keepers to feed dried out weathered oak leaves of all oak species to their roaches. I've been doing this for years, and all my colonies are still doing great, generation after generation.
Stuart, I think the heating system looks okay. You have done a good job there. The exposed insulation may become a problem. George will push off the walls to turn around, and sometimes he will want to dig a little before going to bed. When he does his spurs will rip into that insulation. Perhaps some plywood panels could be fitted that would protect the insulation.
I'm SOOOO glad you posted this thread. We are getting ready to make our outdoor enclosure over the next 2 weeks and this thread answered several of my questions. We were going to use rebar, so I'm glad I read this first. Thanks!!!!!