where does the pound shop buy their stock?

Cheap imports, usually, especially from Germany and Eastern Europe.

I came across a packet of Weetos which weren't chocolate. They didn't look right! O_o

The 50p Wholesalers

Quite possible from port sales ( good imported and not collected), over runs and bankruptcy sales. Although, I only shop there once a year (only being in England then) and the sales of chocolates seems to be pretty much the same!

They import manufactured goods from china, where labour costs are very low- the Chinese Government puts prisoners to work.

They get food products which are trial versions and discontinued stock, Also as they buy in bulk they negotiate better deals with suppliers.

from the 50p shop

Isnt it like stuff that maybe the box is a little damaged or maybe a little default thats why its cheaper

It's often foreign, so it's imported. Although, when you go to warehouses / cash and carry's, the bigger the bulk you buy, the less it costs.

the 99p shop!