Quick update. As it was almost 3 weeks since they signed for my letter I decided to chase them up. Apparently it was an oversight not to send me an acknowledgement letter (not really surprised there) but I need to sign a consent form so they can go to mum's GP, waiting for that to arrive and I will send it back. After that they said it will take approx another 5 week's to finish investigating. They have started investigating tho apparently.
I'll update more when I get it!