Before making a formal complaint or getting others involved, try to discuss the problem with your neighbour.
If you’re worried about approaching them, write a letter, explaining the problem clearly and sticking to the facts.
If the problem affects other neighbours, involve them as well. It can be easier to settle a dispute if the complaint comes from a number of people.
A tenants’ association might help if you’re a member of one.
Get practical advice from Citizens Advice to deal with common neighbour disputes, like noise and rubbish.