Ok, my dad checked out the helmets and this is what he came up with:
"I don't believe they are German helments that have been cut down. The crown is too round. The British had what was called a dispatch riders helment that was round and came down to about the top of the ears. They could have taken some of those and added the skirts to them. Or they could have moulded some plastic or fiberglass helments of their own design. The British dispatch riders helments are not as collectable as the German helment is, so they would not be destroying a collectors item."
Hope this helps...