John Stephens 
The Raising of William Wallace, Junior [EPUB ebook] 

The main character, William, is a boy born to a hopeless single parent in Glasgow, Scotland, unwanted and largely ignored. Life is always a struggle for her. In the course of time she dies, leaving William with the man she had been living with. William is mistreated and bullied, and eventually runs away from home, penniless and with no idea where to go. He hides in a lorry going to London, where he begs in the streets for money or food. One day he meets up with a couple who are planning to make a documentary world-wide on animals and creatures in their habitat.
The two people he meets in London, Jim and Anne, can see a potential in William and agree to take him on as an apprentice. Anne is also a teacher and spends much time helping William with the education he has missed, and he proves a willing learner. They travel to many parts of the globe, Zambia, Botswana, Christmas Island and other places filming and making notes, during which time they have a series of adventures.