Pets at Home are sooo ****! I have a friend who worked in a holistic base dpet shop, and had an interview with Pets at Home, but said they basically want to reteach you what you already know. i.e my friend is HUGELY knowledgeable about small animals ..rabbits hamsters cavies.. and they wanted to reteach her their care.. but that is because the standards they have for care are often more 'commercial' than care based. although of course there are industry standards to meet.
Dont let them think you're a know-it-all, show a passion for animals and a willingness to learn.. but if they think you already know better, they are less likely to hire. I mean.. they sell horrible horrible food for christs sake!