@MagicFox
If (God forbid) a Russia-NATO war did happen, we’d be fighting in Europe not the UK, and the UK would be a target as part of the alliance
IMHO the last part of your comment is really important.
I'd agree with the commonly held view that we are not going to see Russian tanks in London but that doesn't mean the UK population would get a free pass and could sit this out watching the war on TV.
On paper at least a couple of arms of the Russian military have the capability to inflict some physical damage on the UK mainland with conventional weapons, albeit probably not for a prolonged period.
It has to be said that if Russian rearmament continues that capability could increase.
I don't think conscription into the Forces, certainly for a short period of service, is the complete answer (for starters it takes too long train for the really pecialist roles) but I do think a case could be made for mandatory training for civil defence and associated type roles.