Who employs the managing agent, i.e. who owns the property? Are you in a block of flats or a house? I think if you can identify the chain of command on this and who exactly is responsible for the properties it will give you a good starting point. The use of managing agents implies the the porperty is rented or leased, so can you check the terms of the rental or the lease about creating a nuisance or similar.
If you can get some of these answers it will give you some possibilities to attack along another route, but the advice you have been given so far about Environmental Health etc is good and should also be proceeded with.