Hi there,
I was adopted more or less from birth in 1981, so not sure whether this period is the one you want to know about, but I have no problems talking about it.

I have a birth certificate both in my adopted name AND the name that was registered just after my birth. For instance on the BMD records only my first registered name appears, and not my adopted name that I was given at 9 months old.
I didn't know my birth name but sent off for my original birth certificate to the GRO using my adoptive name and a few other details.
Legally my name is my adoptive name as this over-rides the name I was given at birth. However my first birth certificate will still be on record and an official document.
Hope this helps you a bit. Feel free to PM me if you think I can help you any further,
All the best, Em