I am an Iranain national coming next week to Shanghai for exhib. can I also come to HK for 3-4 days?

I am an Iranain national coming next week to Shanghai for exhib. and take part as 2 Chinese factories Iran agent in Shanghai Textile Exhib.
can I also come to HK for 3-4 days, before going back to Iran from Shanghai? I already have Chinese Visa and this is the 6th time I am coming to China during past 3-4 years.Do I need visa, if so, do I need to get it from Shanghai, or in HK Airport?
(I used to live and study in UK as a post graduate and had an ILR)

Many thanks for your guidance.