What should a young Muslim man do regarding his friend who drinks alcohol and uses shared household items for that purpose, especially since they live in the same house in London?

You must forbid your friend from drinking alcohol, reminding him of Allah and His punishment. If he persists, we advise parting ways with him. If that is not possible, there is no sin, but it is forbidden to sit with him at a table where alcohol is consumed. Regarding cooking utensils, it is best to have your own separate utensils and prevent him from using them for forbidden purposes. If you are unable to do so, there is no harm in using them after washing them.