Mayo,
The first thing that came to mind he said was that ,had a military grade nerve agent been used, both the Skirpals would have died instantaneously.

No.
"While the chemical would take effect “almost instantaneously” if inhaled, Mr. Kaszeta said, it would work much more slowly, perhaps over a matter of hours, if absorbed through the skin. The agent is activated when it comes in contact with water and would be absorbed through the pores, slowed down by subcutaneous fat, Mr. Kaszeta said.
At first the effect would be felt locally, around the point of exposure.
Once the chemical entered the bloodstream, it would cause the victim’s muscles to go into spasms, pupils to shrink to pinpoints, and breathing to become very labored, said Alastair Hay, an emeritus professor of toxicology at the University of Leeds. At this point, the victim’s life could be saved only by the administration of atropine, which counteracts the agent and allows the body to metabolize it."
https://www.nytimes.com/2018/03/13/world/europe/uk-russia-spy-poisoning.html
Atropine is readily available in AandE units.

Steve,
On top of that we're expected to accept the assertion that stuff that has been around for over thirty years has never been anywhere except in Russia and couldn't have been made anywhere except in Russia

These things are developed and held in great secrecy.
If they have lost control of it they should say how and who to.

Steve