Do you really know the noises are coming from these specific neighbours. (In a high density area, sometimes noises from elsewhere turn out as the problem.)
This is a very relevant point and and a phenomenon I have experienced myself – I was complaining about noise from renovations I thought were happening in the unit above. But it turned out to be empty and the flat diagonally down one floor, below the one next door, was the culprit.
I highly recommend listening to our chat with Brent Clarke in a recent podcast, when he described how using WhatsApp helped to track down late night shower noise – and result in a fix. If nothing else, contacting people who have also heard and been disturbed by the noise can only strengthen your case if you do go to the tribunal.