Regarding the spy in a bag -- the person involved was a GCHQ mathematician seconded to the SIS and studying Russia, whose "naked, decomposing remains were found in the bath of the main bedroom's en-suite bathroom, inside a red sports bag that was padlocked from the outside, with the keys inside the bag. [...] Inconclusive fragments of DNA components from at least two other individuals were found on the bag. A forensic examination of Williams's flat has concluded that there was no sign of forced entry or of DNA that pointed to a third party present at the time of his death.

Scotland Yard's inquiry also found no evidence of Williams's fingerprints on the padlock of the bag or the rim of the bath, which the coroner said supported her assertion of "third-party involvement" in the death. Metropolitan Police deputy assistant commissioner Martin Hewitt said it was theoretically possible for Williams to lower himself into the bag without touching the rim of the bath. A key to the padlock was inside the bag, underneath his body" (See https://en.wikipedia.org/wiki/Death_of_Gareth_Williams)

It's absolutely mad, but remember this happened in 2010 -- before Russia did many of those bad things you mention. It wouldn't surprise me if a combination of political pressure and police incompetence made this go away.