Well, I don't live in the UK and as an ex-gay man who came out in the late 60's and lived an openly gay life without suffering discrimination I find the argument that society has caused the instability of gay relationships ludicrous. I don't know of one gay relationship that broke up because some preacher called gay sex a sin. I have seen gay relationships break up for promiscuity, lack of trust, money, physical apprearance, and all the same reasons heterosexual relationships are terminated.
Ever-straights who choose to live together without getting married are subject to the same "inequities" you are complaining about. As to fear of exposure; I never worried about it and neither did my gay friends. Yes, I know that some gay's have been discriminated against, but so have unmarried straight couples, Asians, Blacks, and every other ethnic group you can name. However, those who have succeeded have done so through self-acceptance, education, and working within a system not trying to redefine the system.
I know a few lesbian and gay couples who have chosen to committ to their relationships in spite of our society and have been together for years. Why? Because they work at it, they could care less what society thinks and simply live their lives. If societal acceptance can alter a relationship you need to look to the relationship not society.