Was it me, or was her accent changing all the time?

At the start she sounded very english, then when she was getting excited and talking about "the raggedy doctor" she sounded very Irish, then shen she was in it a bit later on, back to English again??

Any idea?

She's Scottish!

Her accent is an odd mix of Scottish and a cultivated English accent.

She's always spoken like this,

Best way I can think of to describe her accent is "slightly mad Auntie who lives in the Highlands."

Thats not a bad thing btw. The world needs more mad Highland aunties.

Did anyone else notice her hearing aid?

I loved Annette Crosbie....from ever since she played the fairy godmother in 'The Slipper and the Rose'!

I liked Crosbie's character as well. I'd like to see her
return in DW.

She's a well spoken Scot, not Irish, not English or anything else.

The hearing aid wasn't a prop, she was wearing it in Hope Springs last year too (in which she starred with Alex Kingston aka River Song).
"slightly mad Auntie who lives in the Highlands" - yep, love it!

She is in her 70's now isn't she?