Let's say one thing loudly and clearly. This is not about preserving a supposedly democratic legacy inherited from the British years against the encroachment of big bad communist China. During 156 years of British rule, colonial authorities did not find it appropriate to implement universal suffrage in Hong Kong (except as a last ditch attempt by governor Chris Patten just before the handover.) While the possibility of extending electoral rights to the local Chinese population was raised already in the 19th century by isolated voices, the prevailing racist considerations were that Chinese culture was incompatible with democracy and that the Chinese were somehow ill prepared to decide their own matters. Later on, this was only enforced by the Hong Kong tycoons who thought that implementing universal suffrage in Hong Kong would lead to chaos and economic collapse. These views never really disappeared. This is why claims that Hong Kong is not ready for full democracy or for un-guided free elections by sinister politicians the like of Regina Ip stem from a self-hating and fundamentally racist perspective and are an utter disgrace for people in public office.
Had universal suffrage been the norm in Hong Kong at the start of the handover negotiations between Margaret Thatcher and Deng Xiaoping, there is no reason to believe they wouldn't have been among the realities guaranteed for the first 50 years of Chinese rule, alongside the free capitalist system. The truth is that Britain had absolutely no concern regarding Hong Kong people's rights after the handover, with the exception of those that allowed British business to go on with its former colony. And while the British government has now a moral obligation to speak in defense of Hong Kong people's democratic aspirations, given its general commitments during the handover negotiations and given that it is ultimately responsible for this state of affairs, Britain can not dare to speak for Hong Kong from a self-righteous position! It can only do so with the humility of a country that has hardly done a better job at serving the interests of its own subjects than China does. Democracy in Hong Kong was not given to us by Britain, it won't be given to us by Beijing, and it won't be given to us by the Hong Kong leadership. Democracy in Hong Kong can only be built by Hong Kong people!