Oops! That's Andrew (not Alan), sorry,
I've had a look at the info I have for Barbara and can see that her record of marriage gives her mother's maiden name as 'Wishart' as you say. However, her birth record gives it as 'Brown', so not sure whether her mother had been previously married, or, if because her mother was deceased at the time of her marriage, Barbara may have been mistaken in her info.
The former seems more likely but will need to look into it.
Regards Eliza.