Hi Catherine, i think there are grants available. However, i am in Scotland and I did not manage to get any meaningful help towards building an extension to our house which sounds similar to what you want, downstairs bedroom, downstairs bathroom. My situation was complicated a bit by the fact that we also wanted to extend the kitchen and my daughter needs a bigger bedroom, but I won’t go into details of that.
The best I could get was that they would give me the cheapest thing that would help me, which would have been a thru floor lift. It was means tested and I would have had to contribute money towards something I didn’t want. It wasn’t what I wanted but you might be happy with something like this.
However, I do know that work to make a house suitable for a disabled person is vat free and at the moment we are looking into what saving can be made from that.
Sorry, I’m not much help really but I’m sure others will know more than me.