As one of those involved in organising the Birmingham Bisley, there was some initial concern about the declaration, but it is nothing onerous and it does not ask for specifics. Therefore, any load data remains in the privy to the person signing the declaration.
All it asks is that the shooter specifies which calibre is being used and which source the load data came from. For example, I stated .308 and the data source was Quickload and the Berger reloading manual.