Pls Suggest Types Of Hair Extensions That Would Sell Fast In London And Buyers!

Hello,

I would be travelling soon and a colleague advised me to buy hair extensions for sale. For those in London, can u advise on types of hair extensions that you guys use often,. Hair extensions that are in high demand and would sell fast  e.g expression, and types of weavon e.g darlyn yaki, noble.
Who are the potential buyers??
In shorter words, what exactly shuld I invest in, thanks for your contribution