Ok, double checked my uni notes- your kids would take everything detective as you and DP are not married. That makes it all doubly important since, if they were under 18, someone else would be administering their affairs. You could use your will to nominate who that person would be, otherwise someone would be appointed by the court. Your house may be in negative equity now, but there may come a point where it isn't and it could be worth something to your two.
I would advise you in the strongest possible terms to get life insurance. My eldest two children's Dad was killed in a motorbike accident in October 2005. I was effectively widowed at 25. We were both covered by life insurance but, because we were so poor and struggling to feed the four of us, in the prior June I cancelled it. Instead of having £100,000 to look after me and the kids, I had nothing. I was a SAHM and so after trying to cope for 2 months on Income Support and Child Tax Credit, I had to get jobs. I ended up working five part time jobs to fit around school and nursery to make ends meet. Things improved slowly, and then much more when I met who is now my DH, but it was still a very hand-to-mouth existence. I enrolled at uni because I never wanted to be that poor again, and I see my degree as an investment in the kids' future, but it has been a struggle that I could have avoided. I haven't a house, but have insurance as I want to make sure that whoever is looking after the children have the funds in place to do it properly.
Ok, you may consider this lecture over 