So, after watching one last night and one tonight I can conclusively ... conclude that JLM completely inhabits the role of Creature but is too wet conventional in looks and manner for Frankenstein. BC on the other hand is perfect as Frankenstein, cold, distant, but also great comic timing, but really all at sea as the Creature. Incredibly strangely he just doesn't look sufficiently monstrous, or physically overwhelming. And I didn't feel the rush of pity that I did for JLM.
Very interesting adaptation. At first I was frustrated that we missed all the build-up to the achievement of Frankenstein's goal (OP I'd strongly suggest your ten year old waits until they've read the novel first) but I can see that stripping the story down to the bare bones makes it all very 'clean' and easily digestible.
As everyone has said, music and lighting were a triumph. So glad to have seen these at last.