Thanks everyone, for your advice/comments.

When I called her yesterday evening, had to leave a message as she was on phone. Started again, when I reminded her we were due to go shopping today. The secondary issue was she'd forgotten but "had no intention of going anyway". Her attitude was still unacceptable, again saying I was selfish. I countered by saying how can I be when I've taken you to medical appointments etc. Her answer was your brother and sis-in-law think it's amazing what your doing. So why all this aggro?!

Then I rang my aunt. Only told her a fraction of the issue as she's got hearing problems. Her advice was don't desert my mother completely. Just take her to appointments, shopping, etc. My aunt was disappointed that her sister had been running her down to me and I was bearing the brunt of her failure to tell my aunt about perceived unacceptable behaviour. Will be interesting to find out what happened when they met today.

I am moving on. Still intend to go away for Christmas. Must find myself a cosy cottage somewhere!