The UK is not a Schengen country - though I believe the law you're talking about is supposed to apply to all of the EU, not just the Schengen countries.
Have you checked the British embassy or consulate website for the area where you are living in the US? They sometimes post financial guidelines (perhaps for other visa categories) and that might give you some clue what level of financial resources they are looking for.
Cheers,
Bev