literally anywhere unless they specify you have to be 18+
i work at a restaurant ( recently turned 17)
my friends work at schuh, corner shops, dominos pizza, nandos, the white company, mcdonalds, selfridges, debenhams, independant restaurants, chain restaurants, starbucks, michael kors, wagamama, yo sushi etc.
i know you can work in asda, lidl, tesco, costa, waitrose, chipotle aswell. you can try retail but it will be a bit hard to get in.
i dont know where you live but top golf will accept students aswell
buckingham palace accepts people to work for the summer but you apply now and they pay £10 ph (retail, sales, tickets)
beware of independant restaurants. theyll usually abuse you tbh