Ina is absolutely correct, the reason why pet passports are a good example to give to DEFRA is because they are defined by
Commission Decision 2003/803/EC and it is clearly stated that they are to be called "Pet passport" and yet "apply only to pet animals of the species dogs, cats and ferrets." (Incidentally there is your legal basis for saying that Czechoslovakian Wolfdogs are legally of the "dog" ie Canis familiaris species.) That is the sort of thing you need to point out in the cover letter.
I apologize to all those who are not interested for the legal jargon (though some might find interesting exactly how a pet passport is supposed to look like).
Anyhow... cheers.
Dhark