Single entry mistakenly used

I had a single entry visa for China and visited Hong Kong this weekend. Now I cannot return to China (Chengdu) where all my luggage and 10 days of work left to complete is. There is 14 days left on the validity, but no more entries. I get the impression I cannot apply for it again from where I am in HK as I am a British national and resident. What can I possibly do to avoid flying back to the UK.