That title sounds really selfish, apologies. For background. We've been through 7 traumatic years of illness, bereavement and loss ourselves and about to begin a much needed 2 storey extension on the rear of our semi-detached house to accomodate live-in carers.
We have always got on well with our lovely neighbour and we gave her the Party Wall letter to sign a while back after we'd talked through the plans with her. (Already got Permitted Development accepted to go ahead).
Thing is. She's died. 
And I'm sure she probably signed the Party Wall, but she was a bit scatty and disorganised and the letter hasn't made it back to us. Now I'm sure her family are grieving and it seems wrong to ask them to look for our letter just now. But. We are really nervous we will lose our builders and have to postpone our extension 
What happens legally? IF she's signed it, can we start now anyway? She is no longer the owner of the house though. It's being passed to her adult children. And they're all of differing opinions as to what should happen to the house now.
What if she hadn't signed it? Do we have to ask the children to sign it? What happens if they all don't agree? 
Can't believe this is happening..........