Well, if your DM goes into care, in theory they can't touch the house or the capital tied up in it even if she was co-owner. So naturally, any social worker who gets over the threshold will mention to your father that he might like to sell up and move somewhere smaller, that the place is getting too much for him. Which may be true but aint the reason they're suggesting it! It's because the house sale frees up capital that can go towards the funding of the spouse in care.
Otherwise they can't get their hot little hands on it. I guess a family occupying a family home works better too in terms of poll tax going to the council and so on.
This would seem not to apply to your father as you say he owns the property. Of course, if due to some sudden stroke he requires a care home well the property's cash from a sale will go on his care, not sure what your mother gets then, she could outlive him by 10 years you never know. Or he could remarry and leave the whole lot to a grasping gold digger and her kids, so you and your mum are cut out. If he does this in a fit of dementia too bad; marriage trumps a will. He could then be dead in two years and you get nothing.
What else? Oh yes. If both your mum and dad have a fair bit of capital between them, house included, taking it over the million mark, then one of you should leave a will leaving it to the 'kids'. Why? Cos you get a £1m threshold. So if say your mum dies first (not a jolly subject this but bear with me) then without a will it goes straight to your Dad. Fine, except for a) The golddigger scenario, where even all her money goes to 'the other woman' and not you, and b) Even if he holds on to it and leaves it all to you, if it's over a million (that's his life savings, the house, you mum's life savings etc over decades we're not talking millionaires here) you pay a shedload of inheritance tax. If it's under a million, you don't. So if one of the spouses leaves, say, £800K to his/her adult children, they don't pay much if anything on it. But if they leave it to the spouse and it takes it over the million mark, then when that goes to the 'children' they're suddenly having to pay loads of inheritance tax that otherwise could have been avoided.
That is all.