I think that some of the schools have ridiculous requirements and this buying branded equipment as compulsory doesn't really happen in Scotland.
My kids basic Primary uniform is grey trousers/skirt, white polo or school shirt. Those items can be bought anywhere, at low prices. The school does sell branded sweatshirts, t-shirts for PE, gym bags, water bottles, cardigans and jumpers but you don't have to buy these and the kids don't have to wear them. For PE they have to wear black shorts and a white t-shirt. We have the school t-shirts as they were only a fiver each and they're quite nice.
My son has just started senior school and has to wear a blazer. School took a conscious decision not to opt for the expensive woollen blazer and went for a polyester one made from recycled bottles. It was £30 including the badge. I also had to buy a tie for £5. Everything else - white shirt, black trousers, black shoes, black jumper - I got from Asda and M&S. The kids look really smart and the stuff with the logo on it just isn't necessary.