Thanks all for the really helpful comments. It's not easy trying to sort this out only via photos on a computer monitor!

While the trapdoor would be nice, and consistent with the Lee Enfield, I'm not stuck on it. Any suggestions on what the recoil pad or lack of was used on the Lee Speed?

I'm also trying to sort out the front sight ... was the original similar to the stock SMLE, which didn't appear ramped?