This is some information I posted on another thread about this:
You really need to look into the legal/financial aspects in case of death or separation, especially if you have children.
If you have children together, and you separate, there are significant advantages in the financial protection you have if you are married compared with cohabiting.
It's hard before you have children to know whether you will want to continue working or not. Whether you are married or not, if you stay at home for any length of time then you stand to lose a great deal in terms of salary, pension, and the ability to earn as much as you did before you had a career break.
That means your ability to recover your financial position is undermined, and of course your mortgage capacity is diminished.
If you are married, then your contribution to joint marital assets is not only deemed to be equal, on divorce these issues are also taken into account in the financial settlement:
1.The welfare of any minor children from the marriage.
2.The value of jointly and individually owned property and other assets and the financial needs, obligation and responsibilities of each party.
3.Any debts or liabilities of the parties.
4.Pension arrangements for each of the parties, including future pension values and any value to each of the parties of any benefit they may lose as a result of the divorce.
5.The earnings and earning potential of each of the parties.
6.Standard of living enjoyed during the marriage.
7.The age of the parties and duration of the marriage.
8.Any physical or mental disability of either of the parties.
9.Contributions that each party may have made to the marriage, either financially or by looking after the house and/or caring for the family.
That's from the Matrimonial Act, and none of it applies if you are cohabiting. There may be consideration given to the housing needs if young children are involved, but not on a permanent basis.
So, many women in long term cohabiting relationships suffer terrible financial hardship.
It also isn't quite so easy to resolve the "next of kin" issue as some people believe - as we have seen here on Mumsnet - where the parents of someone's seriously ill DP intervened in his health care against her wishes. The term "next of kin" has no legal definition. It is only straightforward if no-one else in your DP's family challenges your status as "next of kin", even if you can show this was your partner's wish.
Even if you don't imagine now that inheritance tax will apply to you, it may in years to come. You would also be ineligible for any contribution-based benefits.
I suggest you read this helpful guide:
www.advicenow.org.uk/living-together/
There are legal agreements you can sign, but they still won't give you the protection marriage will.
www.co-operative.coop/legalservices/family-and-relationships/getting-together/
The other thread is here:
www.mumsnet.com/Talk/relationships/a1394224-What-do-you-do-if-one-of-you-wants-to-get-married-and-the-other-doesnt