It's the same old story of old British empire in every colony, where they will promise but never keep it. They were just hypocrite, the main intention was always that colony should not prosper or challenge British empire in future, after they leave.
Your dislike of the UK seems to be blinding you to historical facts? Or do you have sources that prove these statements incorrect? https://en.m.wikipedia.org/wiki/Democratic_development_in_Ho...
“Records declassified in 2014 show discussions about self-government between British and Hong Kong governments resumed in 1958, prompted by the British expulsion from India and growing anti-colonial sentiment in the remaining Crown Colonies. Zhou Enlai, representing the Communist Party of China at the time, warned, however, that this "conspiracy" of self-governance would be a "very unfriendly act" and that the Communist Party wished the present colonial status of Hong Kong to continue. China was facing increasing isolation in a Cold War world and the party needed Hong Kong for contacts and trade with the outside world.[19][20][21]
1960s Edit China's leaders explicitly wanted to "preserve the colonial status of Hong Kong".[21] Liao Chengzhi, a senior Chinese official in charge of Hong Kong affairs, said in 1960 that China "shall not hesitate to take positive action to have Hong Kong, Kowloon and New Territories liberated" should the status quo (i.e. colonial administration) be changed. The warning killed any democratic development for the next three decades.[22]“
The PRC fought the combined UN forces to a standstill in the Korean war in the 1950s, and the British empire had already fallen apart and was in no shape to fight China then in the context of the cold war.