Hello,
@anonymouse. I wish I had known anything at all about dementia, and how important it was to have the PoA paperwork completed and her finances secured.
A good place to start for an overview about dementia and the different types is the information from the UK Alzheimer's Society.
I'd start here:
https://www.alzheimers.org.uk/info/20007/types_of_dementia/1/what_is_dementia
I somehow on my phone, can't find the other pages I would normally link you to, but this is a good place to start.
I read widely on Talking Point, and that is helpful for me. The Alzheimer's Society in other countries (Canada, the States, Australia, and so on) also have websites with information. I also went to the library for books to supplement online sources
I would look for a support group or carers cafe in your area. Talking Point is a lifeline for me, but my local group is also invaluable. I also attend talks, lectures, and workshops given by my local Alzheimer's Society.
I hope that gives you a place to start, and don't delay with getting the legal paperwork sorted, and most of all, take a deep breath and don't panic. You are in good company here, although I'm sorry you need to be. Best wishes to you and your family.