There are regulations about sale of electrical goods in charity shops - they have to be tested before sale, and I believe they can only sell upholstered furniture if it has a kite-mark to show it is fire retardent. I don't however, know of any regulations about clothing. I used to volunteer in a local charity shop, and if there was no label we would guess at the size. And as teddy says, the shop sold anything it couldn't sell as a garment, as rags, and made decent money from that. I am sure your local shop will gladly accept your unwanted clothes, even without the labels.