Sorry I didn't make myself clear. Before about 1911 the mothers surname was not registered so I looked for children born in the right area and just put in the childs surname, in your case Smith. You will eventually come to births after 1911 when the GRO started registering the childs mothers maiden name. Don't forget you will be tracing males and females, so put in the childs surname and in the box marked 'Spouse/Mothers Surname' add the mothers maiden name. This will show only childrens births registered with the right surname and the correct mother.
If you get any more problems, feel free to ask.
Regards and good luck