UK sanctioned... the staff of the prison in which Navalny was murdered. *hysterical laughter*.
This is the problem, IMO. Unwillingness or inability to hit Russia with harmful hostile actions. Throwing money and military hardware at Ukraine won't be sufficient. Even with massive Western help, we will run out of manpower and\or political stability long before Russia will.
To be honest, it's hard to work out what
proportional direct hostile action the UK could get away with, against Russia. This may only be nominally performative[1], and I agree that it's laughable, but it's arguably better than doing absolute zip.
(And, of course, there's already plenty of other things being done/considered in indirect manner, that we know of, as you point out. Nothing directly linked to Navalny's death, but you naturally wouldn't even expect the wheels-within-wheels set in motion by that to become visible this soon. Perhaps not for a long time, if ever.)
And, TBH, if I heard that these named individuals had somehow died of accidents, I'd not even be sure if it was due to foreign actions (from .ue, .uk, .us or wherever) or as internalised retribution handed down by Putin for allowing a medical incident to remove this valuable trapped piece from play, when he might easily have been planned to have been reserved for some hypothetical future exchange. Putin's a chessmaster[2], and the timing of this event doesn't really seem to help him. If it does, then it's part of an even deeper plan[3] that means all bets are off as to whether anything 'we' do can help or hinder the whole situation.
Considering it objectively (apart from the tragic personal nature of this whole thing, to those involved), I find I really can't get excited about an effectively muted opposer of Putin now being terminally mute. The potential knock-on effects into other theatres of direct/indirect conflict are more important. And everyone's hidden background decisions (because of,
or regardless of, this event) will count much more than the currently public decisions.
[1] Hard to see what discomforts can be extended to people in Siberia. I mean, even if they're the ones in charge of a prison in deepest Siberia, they probably aren't exactly world-trotting oligarchists casually transfering indirectly-converted rubles into British banks, buying from Harrods, etc... Because why would they be doing that and (with all due apologies to those who live there)
happily be posted in deepest Siberia..?
[2] Or tries to be, though clearly fallible.
[3] Provoking the West to make such responses as we see/hope for?