When the UN Embargo on trade with China was announced, in 1950, the entrepot trade dried away to a covert trickle. It never actually stopped, because the British hongs could not see the point of the embargo, and ignored it to the best of their ability. The Hong Kong Government complied with the letter, not the spirit, of the embargo, and local firms who did not have political objections to dealing with the Communists (many did) carried on doing so.
The USA tried to maintain the UN embargo after the cease fire in Korea, and insisted that its allies did so until 1957, when it gave up the effort, but the US maintained its own embargo until 1969.
Not all the refugees arriving in Hong Kong were Chinese.
During the war, over 100,000 European Jews were living in Shanghai, in what is still known as the Jewish Quarter (its never been called a ghetto, to my knowledge, because it isn't one).
There were also the White Russians, who had settled in China after their defeat in Civil War following the Russian revolution - there were even more of these.
The Hong Kong shipping companies were offered UN charters to bring these refugees out of the former treaty ports in northern and central China where they had settled. These charters were snapped up because they gave the company a chance to get a ship into a Chinese port to deliver and pick up cargo that was officially embargoed by the UN, whilst being paid under a UN charter!
This had side effects; most Jewish people moved on to the States, Europe, Australia and even Israel. A few stayed in Hong Kong. The White Russians, who had been most decidedly at the bottom of the pecking order in the Treaty Ports of pre-War China, mostly moved to Australia, but my friend and former colleague S. , two generations older than I, an Australian marine engineer who looked, with great respect, much like the average frog, acquired a wife who, even in her sixties, received admiring glances from any man in the room! In fact the White Russians position in the social scheme of things was generally revised upwards once they arrived in Hong Kong and settled down.
In Shanghai, White Russian men were generally employed as guards, bouncers, and so on and White Russian girls were generally "taxi dancers" - a now vanished occupation - a "taxi dancer" was a girl who worked as a professional dancer at a dance hall and you could hire her for a dance. In other words, nightclub hostesses and so in practical terms prostitutes.
The fact that these were the only jobs young White Russians could get to support their parents and grandparents does not seem to have occurred to anyone. The White Russians had no nationality, just Nansen passports, so they were considered the lowest of the low.
Another sea officer of the great and ancient hong married a White Russian in Shanghai, before the evacuations, and he later had a bad accident in Hong Kong - he lost a leg in an accident with a tram - and to the general amazement of the "respectable wives", his White Russian wife stood by him and looked after him, so the other wives decided that they could invite her for tea, after all. Presumably they had expected her to be a "flighty piece".
The flood of Chinese refugees continued. It had peaks and troughs; this was connected to the political situation in China. The first great wave came with the victory of the Communists; the next wave came with the Great Leap Forward and the final great wave came with the Cultural Revolution.
The Hongs, who had generally left some staff behind in China in the expectation that "trade might pick up again", now realised that not only was that not going to happen, but their staff and their families were in danger as "Capilalist Roaders", "Right Deviationists" and "Running dogs of the Imperialists", and made efforts to get them out, often handing over cash or other assets in order to do so.
When I joined the staff of the Great and Ancient Hong, I was given responsibility for their marine insurances, and it struck me that at some distant date, perhaps twenty years before, these insurance placings had been overhauled by someone of exceptional ability. I asked about this "ghost" whose traces I had uncovered and I was right; my distant predecessor has been a man who had been intended, in the Thirties, to be the first Chinese Taipan of the Hong,; he had remained in Shanghai and had spent seven years in a labour camp, being "re-educated". When the Hong eventually got him out, he was a broken man, with the shakes, and he was given the insurance job because it was intellectually challenging but did not demand any serious decisions, which he was no longer able to take.