Paint that could be reused can be taken to some of north London's Reuse and Recycling Centres where it can be recycled. However, at present, due to COVID-19 restrictions, we cannot guarantee that all of it will be reused.
If paint is too old to be reused, it needs to be disposed of as hazardous waste. If you live in Barnet, Camden, Enfield, Hackney, Islington or Waltham Forest, use the corporation of London Hazardous waste service. See their website.