Very possible, I think Emmerdale need to address Moira's mother, it was always implied that she was quite wealthy and disproved of her relationship with John. However no idea why she wouldn't come to her granddaughters funeral.

I remember a Christmas scene where all of the Barton's were on the phone to Moira's mum. They were all laughing but they were glad to say goodbye! Surely someone has told her and Nana Barton though? Seems very strange that they haven't even been mentioned!

When Mpoira needed money for the farm, she asked her mother for a loan, but this was refused. Perhaps this is why Granny ? is not at the funeral. Is John and James' mother still alive in the storyline?

I think so. They used to often mention Nana Barton and there's been no word of her demise.