My wife and I just returned from a 15 day holiday specifically 'tailored' for us by Citalia, through Thompson. We spent 5 days in Sorrento, 4 in Rome and 5 in Viareggio. Air flights, private car pick-up and first class rail tickets all arranged by 'Citalia and all went without a hitch - a great holiday.
About the Hotel Santa Constanza - only B & B accommodation available, but breakfast very adequate, consisting of ham, cheese, bread rolls, quassants, fruit juice and coffee etc.
Twin room and en-suite bathroom on first floor was a good size, clean and comfortable, but the wash basin had to be drained slowly or the waste water would rise from the centre drain cover in this 'wet-room' style bathroom. When we first arrived we were given a double bedroom on the 6th floor which was 'smelly', miserable and dark, but as we had booked a twin they swapped us to the 1st floor. Also the lift only goes to the 5th floor - so if at all possible try and avoid the 6th floor.
Staff and porters friendly, but I had to ask for the air conditioning to be switched back on when returning in the early evening on 3 days, as all of the air-conditioning in the the hotel is switched off at about 10.30 hrs.
Hotel is a good base to explore Rome. Exit the hotel and walk to the right for a about 10 minutes to the Metro station. Metro very easy to use with only two lines of travel. A 4 Euro ticket gives 24 hour use on Metro and buses.
Mid-way between hotel and Metro station is a pizza/pasta restaurant with reasonable prices. And across the road a supermarket.
Leave the hotel and walk to the left for a few minutes and you will come across a friendly cafe where you can eat sandwiches cakes and beer. Further down the road is a McDonalds.
Highlight of our stay was a pre-arranged guided tour of the Vatican/Sistine Chapel. Also went on a guided tour of the Colosseum and Palatine with a local tour operator who approached us as we left the Colosseum Metro station - this was also worthwhile. Food very expensive local to the Vatican so avoid this.