Hi there, when I had DS in 2006, I opted for St Johns. This was because we had heard stories from various people that the Royal Infirmary was very short staffed so would only admit you when you were just about to give birth and struggled to provide decent after care. However most people I spoke to who went there had a good experience and when I went to visit my friend after she gave birth to DD2 I was very impressed with the room she had.
I found St Johns to be good. They have a number of rooms with big baths for water births. The night I gave birth there were a lot of staff available and when i ended up needing an emergency C-section due to complications this was arranged very quickly.
I stayed for 3 nights and it was clean and the staff were nice. Food was lovely although you had to make sure you were in bed when it came.
It won't make a difference to which midwife you get dependant on the hospital.
When I was pregnant we were able to arrange to see the hospital beforehand which helped in terms of the big night itself because the surroundings were familiar.
Don't know about the scans I'm afraid.