Hello Sharon T,
The Inspirational China part of your trip is full board so you only really need to budget for extra drinks,snacks, souvenirs and discretionary tips. The Hong Kong part of your trip is B&B so you will need to think about budgeting for lunch and dinner. As a guide, Beijing & Hong Kong are generally cheaper than the UK so if you were to budget as if you were in London, you should be fine.
You can exchange your money in China in hotels and larger stores. In Hong Kong, most foreign currencies and traveller's cheques are easily changed at banks, hotels or moneychangers. If you prefer to change your money before you depart, most banks and post offices are able to order currency for you.
Kindest regards,
Julia