deed of trust

Hello, My dad left my mum myself and my big sister when i was 2. I've never seen him since. My mum got into a new relationship and had another child with the man who became my step-father. My name and that of my sister were changed by deed-pole to my mums partners name. Several years later my mum and he married. With her new husband she purchased our council house and at the same time she and her husband put the house into trust for us so that we would always have a home. At the time of the deed all my sisters and I were under the age of 18yrs; Since then my mum has died and although my step-father had the right as was stated on the deed to remain on the property until his death it clearly said that if he did not wish to do so he should transfer the property deed into our names. He did not wish to keep the property having met another women who has since become his new wife. He sold our property without our consent using the monies to purchase a new property with his new partner and his mother in-law. What can I do to get back what is rightfully mine? My youngest sister (half) still lives with my step-father but is now 18yrs and my elder sister lodges with her boyfriends family because she has no-where to live. I have been taken in by my aunt in France;