Seadragon,
I see what you mean, I also cannot find a marriage of an Abraham Drake to a Hannah Leach, just the 1854 marriage to a Mary Leach. I wonder whether her name was Mary Hannah and she chose to be known by her second forename Hannah.
It would appear that Hannah Drake died in 1868 at the age of 40. There is the registration of the death of a Hannah Drake in Bradford in the Jan-feb-mar quarter, Volume 9b, page 105.
It then appears that Abraham remarried in 1869 his second wife being Elizabeth Redman.
Maybe the way forward would be either to order the 1854 marriage certificate for Abraham Drake or one of the three childrens birth certificates, which should include their mothers maiden name.
I am sorry that I have not really been of much help to you. If I can be of any further help, please just ask.
I know what you mean about there being a lot of Drakes and Leach's in the Thornton area. I have both families in my family tree and I am also finding it difficult working out which family belongs to which.
Best Wishes
CJL