Hi, and congratulations on finishing your book! I know how difficult it is to reach the point where you can say, "It's finished".
I'm Russell, an Australian and I've just semi-retired to the Philippines. The most relevant of my skills for your project are my excellent English language skills. I have a PhD in Applied Linguistics (TESOL) and ten years of teaching English to non-English speakers. I spent over seven years in Ukraine, a year in China and almost two years in India, all teaching English and editing/proof-reading. I also type at 80 WPM, but I get the impression that this will be more editing, so typing speed is not all that important.
When teaching internationally it is vital to have a good grasp of UK and US English. While most people know that the spelling is different, there are also some differences in grammar.
This is my first proposal, so I don't have any 'Reputation' yet. I hope that doesn't discourage you.
Cheers,
Russell