I wonder what the escalation would be if Putin gets fed up with UK playing the big man and lobs a few conventional cruise at London.
If, by 'playing the big man' you mean coordinating and encouraging an international response to the unprovoked invasion of a country by a horde who's war crimes sicken right thinking people, then bring it on.
I realise it's fashionable to denigrate your own country for some but I wish they'd try to face reality.
In economic terms..
Top countries by GDP (worldbank)
United States: $20.89 trillion
China: $14.72 trillion
Japan: $5.06 trillion
Germany: $3.85 trillion
United Kingdom: $2.67 trillion
India: $2.66 trillion
France: $2.63 trillion
Italy: $1.89 trillion
Canada: $1.64 trillion
South Korea: $1.63 trillion
Russia: $1.48 trillion
Brazil: $1.44 trillion
Australia: $1.32 trillion
Spain: $1.28 trillion
Indonesia: $1.05 trillion
The UK is the 5th largest economy in the world and the 2nd largest in Europe in terms of GDP Our per capita GDP is $39,229 against Russia's $9,972
In military terms
Whilst Russia has enough nuclear missiles to destroy us a 100 times over, we have enough to destroy them once. Once is enough to deter. The Russian forces have been exposed as corrupt, ill-disciplined, ill-equipped and inept. We may not have the numbers of China or the sheer resource of the USA but I reckon our forces are far superior to Russia.