I presume you have the full text of all relevant specifications available, which I do not have.
When someone asks to have an item supplied to an older standard, it is either a practical reason (for instance to replace an older valve), or a pure lack of knowledge of newer standards.
I would advice you to ask for the specific reason to supply to the BS 5155, and which criteria have to be met. If this is about building length, body form, or how to fit between counter flanges, I would take special care to get exact data and measurements.
Generally a BF valve could be with or without threaded lugs, steering holes, flanged ends and to non-standard building lengths, all this apart and in combination with pressure classification for different sizes varying from producer to producer.