Fiona... I see your message is a few years old but I see you're still active on this Forum. I left a message for you on RootsChat but seeing you've mentioned Isabella Corlett here, I thought I'd carry my thread over here.
I'm not related to your Corlett family but my father's first marriage was to a Katie Corlett and I think she may have been your Isabella Corlett's daughter. Our Katie was born about 1880, married in Salford in 1903 and died aged 25 in 1905 at St Mary's Hospital in Manchester. Their 1903 Salford marriage certificate is not too informative but says her father was John Corlett, deceased. There was no place of birth.
My father & Katie had one daughter in 1904 and, a year later, Katie died of "post operative shock, acute intestinal obstruction, pregnancy and intestinal adhesion".
I mentioned in RootsChat that their daughter's name had interesting links to your Corlett family in that she was named Ellie Isabella Sayle. You've mentioned Isabella Morrison and I've seen from the census records that Ellen Jane Corlett was another of Isabella's daughters. So your Corlett family names fit into the naming of Ellie.
You can find mention of my genealogical search for Ellie and her descendants elsewhere in this Forum.
Do you think that these two families are the same? All I've had access to is the census records and the clue that John Corlett died between 1891 and 1901. Obviously he had a daughter named Catherine (Kate, Katie) who was born about 1880. Filtering through the census records led me to this Corlett family.
Are you descended from another of Isabella's children?