Wow how times change. This morning DH took a call from SD30 (from whom I've been estranged the last nearly 4 yrs).  She and her sister SD29, went to BM's place on Christmas Eve, but only lasted a day and a half there. They ended up having a massive argument with her yesterday night and leaving at midnight to drive 2 hours back to SD30's place in London.  
The reason for the argument?  When they arrived, the house was like a pigsty - absolutely filthy and untidy.  The SDs were never that keen on cleaning and tidying, but one of them mopped the bathroom floor before they felt they could use it, so it must have been bloody bad.  But I think the worst thing is that BM had bought herself an Irish wolfhound puppy which keeps trying to eat her 2 cats. BM likes to indulge herself and never thinks things through. There is no way she is up to looking after and walking such a large dog.  I think the old triumvirate of dysfunction is finally breaking up - partly due to the fact that SD29 lives in Devon, BM lives near Cambridge, and SD30 lives in London.  But more because they are finally acknowledging what an irresponsible nightmare their dear mother is.  As I said in the title - SD30 described her mother as unhinged.  Haha - I have always known this about her.