Lots of excellent advice here.
From my own perspective, mam had respite care in 2 different homes, which made our decision easier.
Both were good, one was very new, excellent facilities, all mod cons etc, the other a converted old house, not as many facilities, smaller.
We actually plumped for the smaller home. Mam was happy and well cared for in both but found it easier to make friends in the smaller, slightly shabbier home. As she is very social this was an important factor. As someone else mentioned, the 'atmosphere' here is lovely, more home like, less institution, which suits her. This home was also awarded an 'outstanding' in the care category of the cqc report.
So my suggestion would be, try respite somewhere first, if at all possible. If not, which was the case in one of our other 'possibles', the management there suggested mam went for the day, have lunch there etc to see how she liked it, said dad could go too if he wanted. This seems like a good option also to get a feel for the place.
I wish you well in your search
Xx