Are there any actual wholesale stores for cake supplies? ?

I am a cake designer and patisserie chef and have had my small market stall for a few years. I want to expand my business and get branded packaging and so far anywhere I’ve contacted charges insanely high prices for customised packaging. My design is just one colour, and pretty straight forward. I’ve even thought about using a sticker on normal white boxes for my products. But I don’t even know where to find decently priced bulk order cake boxes. I’ve been trying to look for a wholesaler similar to makro that only specialises in cake supplies where I can physically go to, but don’t know any around London. I would be grateful if someone could help point me to the right direction! 

Thanks again!