to learn about British guarding Napoleon, I would start with books
written about Napoleon on St Helena, because it is an easy place to look.
On Google Books for example, there is a book by E. L. Jackson. It was
written about 1850 and talks about Napoleon. It does not list every
soldier, of course, but there are some mentioned. Mostly, it will provide
an understanding of what it was like. There are other books as well.
this is just an example. Look in WorldCat for more books.
If you are looking for an officer, they would be listed in Hart's Annual
Army List, also available online.