[pneyrinck]

"we've had the problem at the annual screening in a local cinema where the compiled Blu-Ray disc has required Dolby encoding"

Can you explain in more detail about this? Using Blu-ray at a local cinema is not a standard practice as far as I know. Were you using DVD at the cinema before? If you put an AC3 soundtrack on a Blu-ray it should work as well as a DVD. You will need to provide a lot more details for folks here to help.