The common uses of these would be 'rotten to the core' and 'chilled to the bone' (' to the backbone' doesn't exist) Using a noun instead isn't wrong, but it doesn't sound very natural or modern to my ear. I wouldn't say any of these, but the best of the three would be 'an Englishman to the bone' or 'to his bones'. but it sounds a bit old-fashioned and even mildly offensive as it relies on a stereotype, which is fine if that is the purpose. You can also say 'an Englishman through and through' but that's also somewhat old-fashioned. Colloquially, you could simply say "He's very English"

Hello Aud, In this context, you would probably write "He is an Englishman to the bone." You could say "to the core", but that doesn't sound quite right to me. "To the backbone" wouldn't be correct. Backbone in that sense usually means a person's confidence against a difficult situation. A good army officer might be someone with backbone. It's a personal strength. back

American English: to the core

Hello Aud! Nice to see you. How are you?? I hope everything is fine. I'm Hilary from India. I'm not a native speaker of English, but I'm an upper intermediate level speaker. Right now I'm looking language friend to practice my speaking for the IELTS exam and I'm going to take it soon so do you have time to practice twice a week it would be helpful🙏. Pls let me know I'm looking forward to practicing with you 😊