One thing these reports are missing is a Kivelidi case. In 1995 the same agent was used by Georgian mafia to murder a Georgian businessman in Moscow. His office manager and coroner examining the bodies also died. Moscow police found the laboratory behind the agent was neglected by the military after Soviet collapse and at least two employees stolen the agent and sold it to numerous known criminal figures in between 1992 and 1995. It could easily end up at Porton Down.
Since the feckless British are refusing to turn over a sample of the chemical agent used, this can't be verified.
My guess is whatever was used in Salisbury does NOT match up with the known Soviet Novichoks.