It’s mum

My MiL from Stourbridge was Mom.

I like Mum.

Have always hated ‘Mam’, and not keen on ‘Mom’.

Sounds American.

But each to his/her own.

My mother's family came from the West Midlands and female parents were always Mom. My father's parents were one from Cumbria and one from Tyneside and, in his family, the word used was Mam.
My own child always used my name - my preference. I can't understand why the OP or anyone else should be concerned about what other people call their mothers!

I was born and bred in Wolverhampton, considerably before Meera Syal, and never ever used or wrote 'mom, or knew anyone who did. I winced when I saw it in her book.

It is whatever a person calls their mother. Not for you or me to decide.

I am from the Black Country, and always say Mum, my brother on the other hand says Mom!

Geordieland girl here it’s ‘ mam’ or nithing for me.

Fairislecable is correct.

It's chiefly used in America but also found in England used by people in or from the West Midlands.

Writer and actor, Meera Syal, who was born in Wolverhampton, uses it in her book Anita and Me her semi-autobiographical novel, based on her childhood in the mining village of Essington in Staffordshire.

My lovely son in law from the Black Country always says Mom.

Does it matter?

My Grandmother was born in 1895 and she and my mother always signed off cards with “love from Mom”.

Perhaps this is a regional thing from the midlands (UK).

I never respond to anything other than Mummy, Mama or Your Ladyship dahlings