Hi Dora, I've just been in a similar situation to you, however I'm not in the UK so homes can be differently categorised here, in Australia.
My dad had to spend 4 weeks in hospital for an episode of delirium which I believe stemmed from a medication. He was walking with a walker, speaking well, understanding us, not abusive or aggressive in any way, not a wanderer. While in hospital he seemed to lose his mobility, and stopped eating. Mum had been caring for him with additional support from me, but his immobility, size, (6'4") and Mum's health issues meant he couldn't return home, a devastating situation for our family. My sister and I started looking into homes and had some in the area not recommended so had to look a little further afield. While in hospital, Dad had been difficult and abusive with staff who didn't know how to deal with dementia, and an altered sense of reality. Why would he have people wiping his private parts in the bed? This made him very angry, and vulnerable, especially if it was a man since he has a wife and two daughters. He was continent at home but with laxatives and no mobility couldn't get to the toilet.
We assumed, and after the assessment done in hospital that he needed a dementia unit where we expected staff to be trained and adept. We also had trouble with waiting lists and no vacancies but found a more expensive one about half an hour from home with a dementia unit. Dad has been there for 10 days and it's very unpleasant for him, because it has all the most advanced and difficult residents. People wandering everywhere, including in his room which drives me wild, moaning, singing, screaming, blood curdling screams sometimes. All this is upsetting Dad terribly, he can't walk so wandering isn't an issue, he is almost blind so the noise distresses him, he really isn't aggressive, just uncooperative at times, like a child. However, he has high care needs since he can't do anything for himself, needs the lifter to be moved and it terrifies him. This home has many levels of care and the staff seem to rotate about the different sections. It has low care for people who just need help with showering, a dining area with cooked meals, and laundry and cleaning done, it also has high care non-dementia, low care dementia, and high care dementia, where he is now. We asked for him to be moved to non-dementia high care and I believe they've agreed following some assessments. They said there are many non-dementia residents who are difficult, obstructive and cantankerous, so that won't be an issue. There have been countless different staff in the secure dementia unit and they say they work in other sections too so it's not like there's a consistent and small team of dedicated dementia staff, except for the 7-3pm Monday to Friday team, which is always the same.
My long tale (sorry) is to say we thought he had to be in a dementia unit but it has not turned out appropriate for his situation, so see where there are spots free that you can live with, discuss with the home whether they think your mum would be managed well in non-dementia, and then when she is placed, and you see how she settles and copes, keep looking and get her name down elsewhere if it doesn't work out so she can be exactly where she fits. It's so hard to know what any place is like until you're there regularly.
Good luck, Stephanie, xxx