My Mum never said that, but one of my Aunts did!

Not (or never) in a month of Sundays.

Yep - that's what I always thought too!

Well, I'll go to Shields!

is another hoary old quip.

My mother would say “this is between you me and the gate post”. In a hushed voice

My Mum too, Andy.

And, "Did you wash behind your ears today?" And, "Make sure you've to a clean hankie!" when I was going out.

If my mum got really angry, she would say "it's enough to make you spit" if i heard her say that i would keep out the way.

'What would you rather do or go fishing'.
Didn't understand it then or now.

My Mother who was from Fife used to say when she was mad at anything "claw ma whirry wi a whin" and to this day have no idea what it means.

Whirry might mean 'hurry'. Whin in N Yorks (and likely Scots) is the gorse (a prickly sort of bush). To claw: to hold onto?
But, still a mystery.