Don't get me wrong, it may be good. It sounds like yours is.

Most of the manufacturers do try (I believe) to make their BS1088 ply comply with that standard. But often the ones in some countries don't have the QA and inspection systems (and practices) that ensure that their aspirations are fulfilled.

You can get good and cheaper marine ply from these sources. Just don't assume that it will be because it has BS1088 marked on it (GB excepted)