I know said book is released this month (totally buying it, btw) but if anyone else is interested in UK teen parties, I'm a UK teen so I can tell you what I know
Underage drinking isn't nearly as much of a 'thing' in the UK as the US - if you go to a bar and try and order alcohol underage, you just get a smirk and a no - and if the cops bust your house party, no one gets arrested unless they're violent to the officers.
In rural Devon, teen parties consist of two types: the house party and the field party. House parties are most common. No beer kegs or red cups, just a table with little white plastic cups, a couple of spirits (vodka, Archers, bacardi) and Apple Sourz for shots, plus the mixers like cola and lemonade. If there are drinking games it's not just the jocks, everyone participates (unless they're outside smoking fags aka cigarettes, different meaning here). And when everyone's drunk, someone always puts on cheesy S Club 7 and other pop hits from our early 00s childhood.
Field parties: For the classic 'afterprom' party, or some rich, landowning kid's birthday. A big muddy field with a lot of tents and cheap cars (which will be drunk-driven home at 4 in the morning), and a marquee in the middle, where someone's older brother DJs and everyone dances in their wellies (rainboots?). Outside, people smoke, and there is a LOT of naughty goings on. I know 3 people who lost their virginity at the yr 11/sophomore afterprom or yr 13/senior afterprom, and that's just in my friendship group.
People smoke joints, do bongs in their tents, walk around with a bottle of WKD blue (vodka mixer), drinking it with a straw.
This whole post is probably totally irrelevant, feel free to move it to the torches and nappies thread, or ignore it - but if it helps anyone, that's all good