Have always been a 'mum' person - but would agree that it can sound very English.
Certainly don't use 'mummy' though. Don't like both 'mam' and especially 'mammy' as I think they sound unbelievably childish. 'Mother' sounds way too formal and I've always found the first name thing a bit distant or something.
I have a friend who calls her mam by her first name and I hate it, its like they're trying to be friends and not mother & daughter.
I've found recently though that my nieces/nephews are calling my sisters Mom!
I think its the American influence on the sitcoms on the likes of Nickleodeon and other such kids channels.
I called her Mammy when I was a child, then later Mum or Mom (horrible American imitation phase I went through as a teenager). Occasionally use Momma in a jokey way. Mostly I call her by her name though - I used to work for her and hated calling her Mum at work because it sounded so unprofessional. Plus she's my friend as well as my mother so it kind of suits us.
My father is Dad or Daddy but he refers to himself as Poppa for some obscure reason - it's the source of the Momma name as well. I also call him old man and parental unit (male).