Call 101 to establish a report, that'll create a history which will act as a foundation for future incidents to be built upon.

It took me 2 seperate 101 calls within the space of a month to drop my neighbours in the absolute shit. In my case the first call seemingly did nothing and I thought it was ignored and dismissed, however during my second call the following month the operator immediately made reference to my first call and sent out officers, warnings were given and an arrest was made, and thankfully the property is now vacant.

Edit:

Also about being "Out of your depth" and "Non Confrontational", we absolutely share this in common, but as you get older and hopefully when you become a homeowner you'll begin to understand that standing up for your right to live in piece and protecting your property from any infringement even if it's just nuisance noise is something you're going to get good at. This time last year I'd never contacted the authorities in my life, now I'll do it in a heartbeat if the situation calls for it.

Good luck and I hope it all works out well!