i think there were 2 main reasons why civil partnerships didnt signal the end of the universe from the great british public - firstly, the number of "celebs" who immediatly signed up for them meant that the "OK" and "hello" reading masses meant they were too busy cooing over elton or the short bald one from little britain to complain about "ZOMG the gays are out to out-marry us!!!ELEVENTY-ONE!!!"
but also, civil partnerships were introduced for ANY 2 people living together to acquire legal rights equivalent to marriage - examples given included siblings living together, who would have a lower tax burden due to being able to move part of their taxable income so that if one was taxed at the upper rate and the other at the lower, they could both end up at the lower rate - this is something that previously was unavailable to anyone other than married couples.