There are many laws in this country but they are not implemented in real life. I would advise you to go and talk to the neighbour first (if you're still on good terms with them) and ask them if it would be possible to keep the music down. The idea here is that you're not telling them off but rather requesting them to decrease the volume and in most cases diplomacy wins. If you are rude to them or threaten them, chances are they will make more noise just to irritate you more.
You will have to talk to them every time they play music loud until they get the message. This is really hard work but the psychology behind this does work. I remember watching a movie where a man living in a flat was really annoyed that every time his neighbour from the flat above passed by his apartment, he would spit on his wall. The man tried everything and they all failed except one; he would take out a bucket and mop and clean up the mess every time the neighbour spat on his wall. One day (yes, it takes a lot of patience!), the neighbour apologised (guilt striken) and he never did it again.
Getting the police involved in the first instance will create an enmity between your family and the neighbour's. So try to resolve it amicably first and if that doesn't work, then you will have to get the police in when they are playing the music loud. Recording won't be good enough proof here and as you need to show that the music was exceeding a certain decibel for that time of the day.