Writing from real life

I've written a novel, Meeting Coty, which is published by Kings Hart Books (an independent publisher which I'd like to discuss later) and is based on real people. Years ago, my father looked into the spanish side of our family tree and uncovered names, certain facts, events and even character traits for a couple of the characters. I based Meeting Coty on his findings.
What I am pleased about is that he didn't find out too much. If he had, I think it would have been difficult not to feel that I'd taken liberties and not been true to these ancestors who had gone through these events. I would feel as though I was robbing them of their lives and the importance of what they did if I had changed anything. And then it wouldn't have been fiction. And as we're frequently told, real life isn't always interesting.
So. I'm glad I only had the bare bones because then I could make up what I wanted within a true frame work that gave the story a strong base.
Of course, Francois Coty has been written about and researching him was fascinating. He doesn't appear in great detail in the book. This is something else to debate - research and how much to use. Meeting Coty is about the main character, Tessa and her desire to meet the great man of perfume! I have had comments from some people who have read the book that they would like to know more about Coty. So, the follow on book, Leaving Coty, explores his life in more detail while keeping the same characters from the first book.
I'd be interested to know how other people deal with the fact and fiction balance. If we know about a subject, it is annoying to see it changed. The damage that can be done to history. I'm thinking of the Enigma films, the American version and the British one and the bending of facts. I am against this. The Titanic film annoyingly had facts out of kilter, but by basing the story on two fictional characters in that real setting, gave them leeway. But Rose (Kate) spitting? And the middle finger thing? Grrrrr-aghhh!! You can lose an audience by one small discrepency. So, it's the balance. Any thoughts? And yes, I blur films and fiction when I talk because I love both. Now there's another debate...