Brits: How was Christian Bale's accent in "The Prestige"?

Inspired by this thread, but not wanting to hijack. I know Bale hales from the UK, and I see from research he is Welsh by birth but born to English parents. My American ears hear his dialect work in The Prestige as pretty straight Cockney, perhaps a trifle overdone, but I’m wondering how it sounds to British ears.