We would like the whole world to take the most stringent measures against Russia. Removing their membership of Swift would stop all money being transferred in and out of Russia.
Why is this important?
Ukraine gave up all their nuclear weapons in exchange for guarantees by Russia, the US and the UK to respect its sovereignty and territorial integrity. Given Russia's actions it is now up to the UK, and the US to protect them - with the help of all the world's leaders.
Putin has shown that the sanctions enforced up to now lack bite. This is more likely to help the Ukrainian people.