The same cannot be said of society. In the UK we are all, as subjects of Her Majesty the Queen, bound by a legal framework out of which we cannot opt.* Thus where there should be proper equality is in the structure of legal marriage. If there is no difference between a civil partnership and a registry marriage except in the gender of the participants, then there really should be no need for two separate legal entities. This, I believe, is where the government is trying to get to with its recent consultation paper that has stoked up so much controversy.
As for religious marriage? Well, as far as I am concerned, it should have no legal significance whatsoever. A church wedding is a matter between two people and their god - and no-one else. Even the witnesses are really only there for the free booze. After your bridesmaids-and-confetti extravaganza, if you want to enjoy the different rights our society affords to couples over single people, then you should hie yourself down to the registry office, where you can be officially recognised as a couple regardless of the contents of your respective trousers.