Mum is on borrowed time. What do I do when she dies?

[Twinklyfaerieglade]

My mum has been on borrowed time for quite a while. She is 88, not eating, barely drinking and the GP is astonished she is still alive, but says we are looking at a very few days now.
She is still at home thanks to brilliant support from careers, the GP and my dad. Dad has just asked me who he phones if she dies tonight. Obviously I said me, but he then spoke about 999. Clearly 999 isn't appropriate as they cannot do anything for her but who do I notify? Do I phone out of hours?

@Twinklyfaerieglade I just want to send you some hugs, you have already had the advice your asked for in your original post.
I haven't gone through the death of my parents yet, but looked after my husband when he died and it is such a hard thing to go through.
More hugs.