The only thing you can do is put your complaint into writing.
Unless the leak has prevented you from using the room below..and that room is critical for "habitability" (kitchen, for example)..you really don't have any recourse here. Just protect yourself from a possible future claim that the damage was your fault for not reporting it.
If you get a plumber..you will pay for it and you will not be able to recover your cost.
So.. how does having the ceiling paint bubbling effect your use of the place? I know it doesn't look great...but..I don't think it is an issue with habitability...unless it is bring plaster down into your dinner while you are cooking?
Leakage problem is a very big problem.It is very difficult to solve.I think we should take the help of leak detection services for this.They easily find out leakage and help in repairing it.Plumbers don't repair the leakages properly but these services uses new technologies in finding leakage and repairing it.