My DS is 8 next month too! I agree, it’s a difficult age to buy for.
I’ve gone for Smiggle stationary in his stocking (I stocked up during the sale and hammered their 5 for £5!) as even though he’s had all new this month going back to school, it’ll look a bit tatty by Christmas. Also match attax cards, sweets and slime.
For his main presents, I’ve gone for Pokemon cards (you can get box sets on amazon), Lego Classic and Lego Ninjago, a butterfly house thing where you get the caterpillars and watch them develop into butterflies, the playmobil submarine for the bath with some sharks and octopuses and a hapless looking diver, a pair of football boots (he’s just started going training this summer), tickets to a Chelsea game between Christmas and New Year, Pokemon Let’s Go Pikachu on the Switch, Pokemon Let’s Go pokeball controller (had to preorder those two!), Legend of Zelda (switch) and then some merch from his favourite YouTuber (Dan TDM? TDM Dan? I don’t know, the bloke’s an idiot) and then just some other bits and bobs. I’m trying to not twitch, but the playmobil knights castle looks amazing and DS will love it (also I really want to play with it).
Boys tend to play with toys longer though, and mine is an only child so I think he’s going to be quite a ‘young’ 8 if that makes sense, so I don’t know if that helps much.