lib58 - An adoption certificate looks like a birth certificate, but although it gives date of birth, it gives names of adoptive parents and is (from memory) red rather than green of the birth certificates. It also has a heading saying something about adoption.
It's easy to check if your husband was adopted, go to
www.freebmd.org.uk, (as the name suggests it is a free site), put in your husband's name, year of birth - it asks for date range, so just put Sept 1956 to Dec 1956 - as it gives the quarter the birth was registered and someone being born in September, might have been registered in the October-December quarter, and Lancashire for the county. You can also put his mother's maiden name, if your husband knows it. If his birth shows up then he will have been born to his parents. If it doesn't then it's possible he was adopted and given a new name.
If your husband has a passport he will have had to show his birth certificate (or adoption certificate) to get it.
Lizzie