Hello and thanks for using Just Answer.
My name is ***** ***** am happy to assist you with your enquiry.
Under the intestacy laws in 2008 (rules which apply where someone did not leave a Will), your step-father would have been entitled to inherit the following-
your Mother's "chattels" - her furniture, clothes, car, etc. - and a maximum of £125,000.
The rest, known in legal jargon known as "the residue", must be split two ways. Your step-father would have received an income (called a "life interest"), from one half of your Mother's residue.The other half goes to you.
If you wished to progress matters (I don't know how much your Mother's proeprty was worth back in 2008), you shouls instruct a local Solicitor who can check if your Mother did indeed make a Will or not, by doing a search at Leeds Probate Registry, and can also check with the Land Registry in whose name the property is now held (it may have been that the property was in the joint names of your Mother and your step-father, meaning that the property would have passed automatically to him upon your Mother's death. If so, the house would NOT have formed part of your Mother's Estate when calculating how much your step father was entitled to receive).
I hope this assists you and sets out the legal position.