Used mobile phones/Secondhand mobile phones Grade A-C

New business trading original used mobiles phons (grades A,B,C and non working) based in the U.K with a view to selling them wholesale in Hong Kong/ China. Therefore i'm looking for companies in these destinations to do business with (B2B). I have been having some difficulty with both locating companies that purchase used mobiles phones and getting an idea of the purchasing rate, even though most used mobile phones are purchased and sold in China/Hong kong. I will be visiting China and Hong Kong in September. I requires an agent/freelancer for assistance. Look forward to hearing from you.