Britain effectively pulled out of E.U.?

I claim no expertise in the intricacies of Euro politics, but it would seem from the refusal of Britain to join the rest of the E.U. in a treaty to impose uniform fiscal standards, that Britain has effectively removed itself from the E.U. for most practical purposes. Britain's justification, from what I understand, is essentially to preserve plutocracy: i.e., protect its banks and financial sector, the control of which is precisely why the treaty is needed in the first place, so, although not a member of the "Eurozone" anyway, it would appear that Britain has basically taken its toys and gone home.

I guess the question is whether or how long the E.U. as a Great Idea can survive without Britain as a real member.