Oh. In that case I'm sorry to say that there has been extensive work done in that (UTF-8/Unicode) area in every version after 5.8, and that since it sounds like you're using it in a not-really-intended way, you're quite likely to run into problems.

I can definitely see how doing it the way you describe was a good choice a bunch of years ago, but I don't think it is any more. It also sounds like the sort of thing that's a huge amount of dull and fiddly work to change...