I would echo Ros's comment about using the GRO birth indexes to get the mother's maiden name.
In complex cases like this you may have to resort to ordering copy certs from the GRO. The birth cert gives at least the mother's name and if legitimate the father's too. PDF is cheaper than paper.
A marriage cert gives the names of the fathers of the bride and groom and can be matched against their birth certs to make sure you have the right ones. You also get the ages of the bride and groom though earlier ones often just say "Full" (21+).
If you are very lucky a pay web site you use may have an image of a marriage cert, and baptism records can be handy too.