If you want to go to Peking University to study for a doctorate, you basically go to a good school in China to study for a master's degree, and then apply for a doctorate in Peking University. However, compared with the postgraduate entrance examination, it should be much easier to take the exam. After all, there are very few people who want to study for a doctorate, and there is still hope to actively contact the tutor. There are many doctoral students in Peking University, and both undergraduate and master's students studied in non-prestigious schools.
If you want to study PhD in Hong Kong, you should go to Hong Kong to study for a master's degree first. There are two kinds of masters in Hong Kong: research masters and teaching masters. The former has a full scholarship and can accumulate research experience, but it is very difficult to apply, let alone manage this subject. The latter is more expensive, with a cost of about150,000 a year, but the gold content is not high, but it is quite easy to apply. After all, it will be much more convenient in Hong Kong. I think you can consider taking the road of teaching master.
As for the intermediary, I never believe it. Just do it yourself.