If you think it would be beneficial to follow up the midwife lead, the best way to find a midwife is through a midwife. It is not unusual in the states for midwives to practice 20, 30, or even more years, so if England is similar, there is a good chance you may be able to find a midwife who is currently practicing or recently retired who has been around since then. It would take a lot of legwork, but it might be possible to develop a list of contacts and a subsequent records check. After thinking it through, I think it might be most likely that she birthed on her own. Even a home birth with an attendant would have resulted in a birth certificate. But that doesn't mean she never saw a caregiver. So you might want to identify a 6 week period or so which would encompass your due date and ask whether there are any records in which a mother was seen who would have been due during that span, but at some point left care, probably without notification, transferring records, etc. It would be easiest to start with hospital midwives, I would think, as records are more likely to be kept in an archives somewhere.