Thanks Mr. Johnnash.
However i would like to clarify to all who have the same request as mine, that it IS possible to get a SINGLE entry China visa valid for 15 Days in HK, provided that all your documents are upto date: that u have previously travelled to china on a valid visa before; ur passport has no cancelled china visas and that you have a confirmed return ticket or a ticket showing exit from China and a confirmed hotel booking voucher.

I have this information from my telephone conversation with a lady at the Chinese travel affairs office in Wanchai( contact number +852-3413 2424 ) who was extremely helpful and polite.