May i ask if you were born in the UK? To get a replacement birth certificate you can even do it online by contacting the registry office where your birth was originally registered. I had to get a certified copy fairly recently. The original Registry Office had closed down but it was easy enough to find out where my records had been transferred to (the Registry office closest to the closed down one). UK Birth certificates are valid for life.
I have in the past year also renewed my very out of date British passport.......i didnt need a copy Birth certificate for that either. Saying that i did submit the old one so that may be why.
