I don’t think it’s directly referenced in the comic but him and Myria are from around Oxford. However Myria speaks with a more posh accent to make herself sound more intelligent (modern bbc accent or ‘received pronunciation’. She speaks quickly and precisely, giving her kind of a chirpy voice. When she gets mad or otherwises loses composure she gets shrill and her lower class upbringing seeps in. Frost speaks more typical southern and enunciates less clearly. His voice is deeper and guttural than typical due to his large size. He’s also just out of habit normally a low volume, slow talker as he’s not really very naturally outgoing, which makes him sound more menacing than he really means, again because of his size.