In my view Putin is not entirely sane which makes this difficult. Russia has been reduced to a 'side show' on the world stage which I'm certain sits very badly with him.
The UK has nobody with the intellect and subtlety in government to send to Russia. We sent Liz Truss and that was just excruciatingly awful to witness. Johnson probably things he can phone up Putin with a Peppa Pig joke and smooth it all over. The UK has been taking dirty Russian money for years, and allowing Russian oligarchs to set up show (and donate to the Tories) for years as well. We are not blameless in this and it's high time we cleaned our act up.
If he does invade Ukraine (and it seems likely) I think the question is not "Should the West respond with force ?" but more "Can the West afford to not respond with force ?"
Russia, and China, see the Western powers as decadent in the true sense of the word - decaying. Given the reaction to Russia's annexing of Crimea they would seem to be right. There was some pious hand-wringing and little else. China in particular will be watching this very carefully. If Russia invades and the West responds with some sanctions and nothing else my view is they will see this as a green light to take the territories they've always claimed and wanted. Myanmar, Tibet, Taiwant to name but three.
If China takes Taiwan this is very serious. Much of the cutting edge semiconductor manufacturing is in Taiwan - the West would lose this and China would love to get their hands on it as their tech sector has nothing comparable.
If China successfully annexes Taiwan what would be next ? South Korea ?
Both Russia and China are despicable and appalling regimes and thus far the West has turned what is effectively a blind eye to this - particularly with China where so much manufacturing for Western companies takes place. One option would be for the US, UK and EU to collectively cut these countries off from global finance and enforce this. Putin doesn't care about sanctions but this might well be the shot across the bows he does understand.
In many ways the parallels with Europe in the 1930's are startlingly similar. Are we at the Chamberlain stage (Peace in our time) or the Churchill stage though ?
Whilst I accept that Ukraine being invaded is a difficult situation and the temptation is to not respond with force, I think the West has to grow some collective cojones and accept that there comes a point when you have to say 'enough'.