Yes, it’s not the easiest decision to make, hehe. If you have no preference, then perhaps we should go with the show aesthetics as the show fleshed out Lyra’s time with Mrs Coulter a lot more than the movie did? But, really, you can have final decision on that as you’re writing her, and I‘ll choose the matching Lyra.
And as for narrative, I agree with the RP focusing on their time in London and not progressing through the story past that!