The notion that Britain is to blame for the situation is interesting. Sir John James Cowperthwaite  introduced very laissez-faire economic policies in the 1960's (he famously refused to collect economics statistics (such as GDP numbers), as he argued that they'd just encourage technocratic government officials to meddle with the economy).
First, this tells us that libertarian ideas have their limits. They arguably made HK rich back then (but note that many other economies were growing rapidly in the 1960s and 1970s, with far more left-leaning policies; the USA had a marginal tax rate of 70% for the highest earners in those decades and grew just fine).
Second, it is well known that Britain tried to grant Hong Kong more autonomy and democracy way back then, but was thwarted by China in that. Furthermore, the democratic reforms Britain instituted before the handover were promptly revoked by China.
Thirdly, Hong Kong has been a Chinese SAR (special administrative region) for over 20 years by now. To blame Britain for the current conundrum is a bit far-fetched.
Note by the way that several Hong Kong protest leaders have been granted asylum in Germany.