I'm glad someone started this thread. Have been thinking about doing it myself for a while actually. Mainly b/c I have found it to be so curious that so many MN'ers seem to have dp's instead of dh's. I'm wondering if it's different in the UK or if it's just because I live in the southern US which does tend to be more traditional. I only know of one couple who have children and are not married, but I think the children are from a previous marriage.
I remember when dh and I first started dating. The magic of the relationship was so strong that topic of marriage came up fairly soon. For some reason, we both just felt that we wanted to make that commitment to each other, even though at that time we had no thoughts of having children and had both experienced disastrous first marriages with a long period of being single. We didn't actually get married until we had been together for a year and a half and absolutely nothing changed for the worse. It only enhanced our feelings for each other.
Now, having children...that's another story. We're still trying to figure that one out. Seems like everything changes afterward, although my severe PND was a definite factor for a while
Anyway, FWIW, my feeling is that you need to know quite clearly your position legally if you are not married. As YG has so generously shared, it does make a difference. If you have children, I do believe that their future welfare should take priority over everything else.
I haven't read the whole thread, but noticed some of the comments re: cleaning, etc. Before we had ds, dh did virtually all the cleaning, shopping and cooking, as he worked part-time from home and I worked full-time. Now things are a bit different and we share chores.