If you don't have access to a pay site for census familysearch is very good on some years 
https://familysearch.org/search/
Hi Stuckley1
Before purchasing any GRO certificates, -There are free public computer access to online Ancestry.com 'Free Library edition' at most main Town/City libraries for usually a couple of hours a day. If you live abroad ? like Australia, USA, Canada, or New Zealand - a lot of their main libraries will also have free access to Ancestry.com
Also a lot of main libraries are now getting free access to 'Find my past' website also.
When the time comes to buy a birth certificate, contact the appropriate local register office direct off line as they will ask you what you know about the birth to compare to their records first !! - this cuts the chances of getting the wrong certificate.
