The council have made it very easy to report issues with trees via their new CRM system.
This page explains what the council are responsible for and has a link to the reporting page
https://www.havering.gov.uk/info/20013/environment/52/trees_grass_hedges_leaves_and_weeds
This is the link to the direct reporting page
https://portal.havering.gov.uk/treeenquiry-location/
Please try it out.
Further systems will be coming online over the next few months.