JayB
First of all there are a few things to be considered...
1) you cant just get an HKID i mean if you qualify for one then my appologies, but like all paperwork this takes time.
2) if you are to get a place offered with the cadet pilot program i believe that you are allowed to be posted back to the uk only once you have reached the ranking of a first officer and when that comes, it is dependent upon seniority.
further more, once you become a FO, you really should stay in HK so you could gain enough flying hours i.e. with short haul to and back from china, and long haul combined.
once you have done that, then maybe you can consider basing in UK, this is because if you base in UK you are likely to only get the LHR-HKG route which would not gain you that many hours after all...