We would highly recommend staying at the casina. The apartment's location couldn't be better. Moments from Piazza Navona and easy walking distance from the main sights. It was very comfortable and quiet, and though it is a compact studio (as the pictures show) it was absolutely fine for two people. Some bread, eggs etc. were left for breakfast, which set us up for the day.
Fabio was very good with communications, giving plenty of useful information and suggestions for our stay and was flexible around our timings. He also kindly picked us up in his car from where we were dropped by the airport coach after a late flight.
Thanks F&F!