OP is not being unreasonable, she's complaining about consistent antisocial behaviour that happens ALL THE TIME, and Friday night was just the last straw! FFS this isn't hard to understand?
Of course it's not 'illegal' to have a one-off party that finishes before 11pm. But as part of a pattern of behaviour that demonstrates her neighbours are horrible, inconsiderate sods who don't give a shit about anyone around them ... I completely sympathise, OP.
There is so much of this sort of thing nowadays - especially now that everyone seems to have embraced the concept of 'outdoor rooms'. I live next door to people who have friends and kids around every time the sun is shining and the outside temps top about 17 degrees. It's the constant kid-screaming, hollering, multiple dogs barking, BBQ smoke (and weed smoke in the evenings...), or power tools as they're also constantly constructing yet more buildings and structures in their garden (last count, 10!!). None of it (weed aside) is illegal but it's most of the time and we similarly feel we can't rely on peace and quiet in our own garden.
To suggest that we lump it, or find some money and buy a field with a house in the middle of it, is besides the point. Yes, you expect some neighbour noise if you have neighbours, but if you live alongside people, there's a social contract on both sides. Don't be arseholes. Don't have people round EVERY weekend. Don't play your music so loud outdoors that people three doors down can appreciate it. Train your bloody dogs.... etc.