There are no hard and fast rules regarding your financial rights on the breakdown of a relationship.
When negotiating a financial settlement at the end of a marriage there are various factors that need to be taken into account. I am not sure it helps to go through them all as they are very "legal" wording. But basically, a 50/50 share of assets is a very rough rule of thumb, in as much as Judges need to explain why, if they want to move away from that.
Understandably, a lot of people will ask "What if we can't agree a financial settlement" when starting to think about a financial settlement and often the honest answer is that it depends upon what there is and then all the facts.
So, for example, a woman who was married for 3 years, worked throughout and had no children would be entitled to a very different financial settlement to a woman who was married 20 years, did not work but helped her husband who created a very successful business.
And pension treatment on divorce is a very tricky area upon which careful advice is needed so do find a lawyer who is a specialist divorce lawyer.