I am getting anxiety attacks every time I speak to my Mum who has been in a care home for 3 weeks. How can I manage my own reaction better?

What I hear when I read your post is that you feel guilty and anxious, as if it was up to you to make your mom's problems go away and you are failing.
You are not failing. You have done the most excellent thing by making sure she is safe and cared for, whether she sees it that way or not.
You cannot control how she thinks or feels. I would advise you to work on controlling how YOU think and feel. And first of all please realize you (and your sibs) are not at fault and you're not responsible for her dementia and unhappiness.
You are not at fault. They are not at fault.
It is wonderful your mom is starting to allow baths. Let the caregivers work with her and take a step back.

So sorry you are in this position. I also felt the reaction to all this. Three years later I feel so much better. I go to counseling 2x a month. I pay a small co pay charge. My brother seems teflon coated. My heart was breaking for my mother. Her place is lovely and in time she has grown to call it “home”. My mom is 89. Good luck!

Frankly, I'd put some more space between you and her and move to calling every other day, or every three days. Take turns with your brother making the calls, too.

She has Alzheimers, so you can't believe what she says. The mom you knew is gone, sadly, and this is someone else.

You simply can't take to heart what someone who is not in her right mind says. You're reacting as though the things she says are true, when the staff is telling you otherwise. You know deep inside not to believe and absorb all this.

If you had childien, did you give in to their every tantrum? Did you believe every fall was a life-threatening emergency?

Of course not.

This is the same thing here. Mom's wiring is short-circuited, so you need to react as you would to a toddler with soothing words, then distractions. Simply change the subject -- don't ask if you can, just do it.

If Mom is still able to write, get her a journal and tell her to write down how she feels, so she can off-load it when you aren't there to listen. It might prove to be illuminating if you tell her to write in it each day and tell about her day. It'll likely be all over the place, and that might help you understand better how her mind isn't working anymore.

Your mother's behavior is typical for dementia/Alzheimers and wanting to 'go home' goes with the territory. It's more a place in time she's wanting than a brick & mortar building. You asking her for something will not register in her broken brain, which is why she's back to the faulty thinking almost immediately after she acknowledges your request. She can't help it; her brain isn't thinking clearly anymore, sadly. But now YOU have to look after YOURSELF b/c your anxiety is through the roof. I used to internalize a lot of my mother's angst when she was carrying on in Memory Care with her dementia, too, so I cut down on calling her so often. I KNEW she was well cared for by her carers, so why put my own mental health in jeopardy to hear her repeat the same jargon continuously? I suggest you do the same.

I suggest you read this 33 page booklet (a free download) which has THE best information ever about managing dementia and what to expect with an elder who's been diagnosed with it.

Understanding the Dementia Experience, by Jennifer Ghent-Fuller 
https://www.smashwords.com/books/view/210580

Jennifer is a nurse who worked for many years as an educator and counsellor for people with dementia and their families, as well as others in caring roles. She addresses the emotional and grief issues in the contexts in which they arise for families living with dementia. The reviews for her books are phenomenal b/c they are written in plain English & very easy to read/understand. Her writings have been VERY helpful for me.

The full copy of her book is available here:
https://www.amazon.com/Thoughtful-Dementia-Care-Understanding-Experience/dp/B09WN439CC/ref=sr_1_2?crid=2E7WWE9X5UFXR&keywords=jennifer+ghent+fuller+books&qid=1657468364&sprefix=jennifer+ghent%2Caps%2C631&sr=8-2

She also has published a workbook entitled, “It Isn’t Common Sense: Interacting with People Who Have Memory Loss Due to Dementia.”

https://www.amazon.com/Isnt-Common-Sense-Interacting-Dementia/dp/1481995995/ref=sr_1_4?crid=2E7WWE9X5UFXR&keywords=jennifer+ghent+fuller+books&qid=1657468655&sprefix=jennifer+ghent%2Caps%2C631&sr=8-4

Here is a list of useful tips from her e-book I found to be excellent:

The “Dont's”
· Do not reason and argue
· Do not demand that they reason or problem-solve
· Do not demand that they remember
· Do not demand that they get their facts straight
· Do not correct their ideas or scold them
· Do not reorient them
· Do not think that they are being uncooperative on purpose
· Do not think that they really do remember, but are pretending not to
· Do not use a “bossy” dictatorial attitude in care
· Do not act with impatience

The Do's
· Enter into their frame of reality, or their 'world'
· Be aware of their mood or state of mind
· Use few words and simple phrases
· OR use no words, just friendly gestures and simple motions
· Do everything slowly
· Approach from the front
· Wait for a slow response
· Constantly reassure them that everything is 'OK'
· Keep people with dementia comfortable 'in the moment' - every moment
· Maximize use of remaining abilities
· Limit TV or radio programs which they may feel are frighteningly real
· Maintain privacy
· Provide a safe physical environment

Language Needs
· Use short words
· Use clear and simple sentences
· Speak slowly and calmly
· Questions should ask for a “yes” or “no” answer
· Talk about one thing at a time
· Talk about concrete things; not abstract ideas
· Use common phrases
· Always say what you are doing
· If they repeat their question, repeat your answer as you did the first time · Give them a longer time to process information
· Wait patiently for a response
· Be accepting of inappropriate answers and nonsense words
· Speak softly, soothingly and gently

Wishing you the best of luck with a difficult situation.

Perhaps it's best that you limit your calls to just once a week since they are so upsetting to you. And if she calls let them roll over to your voicemail, as I'm sure if it's something important the care facility will contact you directly.
If your Mum was in her right mind you know darn well that she would not want you getting so stressed because of her, so it's time to take a step(or 2 or 3)back and start limiting your calls as they're not doing you(or her)any good only causing you harm.
Your Mum would want you to take care of yourself, so please start doing that.

Alison, your mom is adjusting!

Allowing baths is huge.

Have YOU spoken to the social worker at the home? Perhaps s/he will have some suggestions.

Often we are told to stay away during the adjustment period, but you are already doing that, not by choice.

I would take a firm, authoritative tone with mom. "You are where you need to be right now, mom. I can't do anything about that."

Do you have someone to talk to about your anxiety?

Becomimg anxious every time the phone rings when you have an elderly parent is pretty common. I certainly had it. Talking to a therapist DOES help.

There isn't much you can do unless you move her to a assisted living complex near you . Although then she might complain she Misses England and you would go thru the same loop . She Must be able to make friends where she is . In the Meantime try to meditate , focus on your children. I use acupuncture to relax . That has helped with My anxieties dealing with a stressful parent .