Occurring throughout the play, the voices are a kind of intermediary between the audience and Christopher’s interior state. They report facts, or echo things from within his auditory environment. Their accent should be unremarkable (probably Estuary) unless the thing they are relaying has some particular information conveyed by accent.
I’m thinking here of 32. SWINDON TRAIN STATION, 35. PLATFORM and 37. TUBE TRAIN
For these, the voiceover site https://www.advoice.co.uk/ should provide a rich selection. Here are a couplethat I thought might work for you:
Here’s one model that might fit the bill:
This is an Assistant Principal at New College Swindon. She has a few more of the West Country features, but she reads a bit higher class:
We spoke about her being somewhat more refine, with affectations of class. In this video from the Commonweal School in Swindon, I’ve set the video to start with a blond woman (who I haven’t yet identified). I think she has something of the qualities we discussed:
Ooh! I did find her! Her name is Becca Fidan. She was actually born in Sheffield which is more Northern. Nevertheless, she has many of the pronunciations we hear in Swindon.
WOMAN ON TRAIN
Really this could be anything! I toyed with the idea of her being an American, but I think that might be distracting.
We discussed making her Cockney, and that still makes sense to me.