Nice projects. Wot do you do in your spare time? lol.

I'll have a crack at dating the two commercial actions and others will hopefully correct me if I am wrong.
I've been collecting and actively studying martial Lee Metfords and Enfields for 35 years. I still consider myself a student.
Being a military collector, commercial Lees are something relatively new to me.

I think that the two commercial BSA actions are likely to be post WWI.
If they were 1901 would they not display the LEE-SPEED PATENTS banner?

A VR marking isn't conclusive with regards to date.
Some inspectors didn't get updated stamps for the new monarch right away.
You mention that there are also ER and GR markings?
These sound like govt proof marks? Military barrel?

When you get the chance show us some details of the markings, please, otherwise we are just guessing.
Dating commercial Lees is currently my interest, a new challenge.
They are not always easy peg. Often only to a window of years.
Proof marks can help narrow it down.

The bolt with the chopped dust cover lugs could be repaired.
I have managed to make new lugs and silver soldered them back on.
Not really much stress for them to hold the cover.