Depending on where you are flying from in the UK, flight times in to Hong Kong International Airport vary, naturally. For instance, a direct flight from London to Hong Kong takes between 11-12 hours (approx), but you can also take a stopover flight to break up the flying time. Alternatively, if you're looking at traveling from China to Hong Kong, a direct flight from Tokyo takes about 5 hours, or you could travel by boat and train.
Hong Kong is known for having comfortable and mild weather for over half of the year - with the summer changing to humid and wet (the rainiest months are generally between June and August). The best time of year to travel is between October to March, where the rainfall is low and the temperatures are cooler.
In relation to China, Hong Kong is to the South. If you wanted to travel between the two, it would take around 3-4 hours to fly from Tokyo to Hong Kong.
Hong Kong is a Special Autonomous Region, which means that it governs itself separately from China in all matters, except from those in foreign and defence affairs.
The currency of Hong Kong is the Hong Kong dollar.
Hong Kong Dollars are not accepted in China, and you will need to exchange any spare HKD that you have into Chinese Yuan.