The stuff the Hawkers sell is an unknown liquid that has been proved to be made in unhygienic conditions with water full of bacteria. Some women who have dabbed it on their necks have incurred rashes and infections and as Lotty says the Hawkers pretend the perfumes they are selling are genuine with identical packaging of famous brand. These Hawkers are being dishonest and committing fraud.
D.&.P. is made under very hygienic conditions is sold in many shops all around the world including a London Shop and they make it clear they sell copies.
So, Dave go and try it for yourself and then come back and comment.