Hi Toni
My mum was adopted circa 1943. She/her adoptive parents were given an adoption certificate, on which was stated the adoptive parents names, her date of birth, the date of the adoption, where it took place (ie which court). From memory I can't remember any other details, but it certainly did not contain any details of birth parents.
I decided to try to find out birth details, but once an adoption has taken place, the 'original birth' details are effectively closed. To find out details, I was told I had to get my mum to agree, and she had to apply. My mum has never wanted to know any details, so this was not an option for me. But in reality, I knew her birth mother's details, and was able to quote this to the GRO, along with all other details (date, location etc) so I got the certificate (I wanted to know if a father was recorded). My mother does know I have the certificate, but has never asked for any details, and I have never told her about them.
EeyoreBlue