Many airlines now permit you to book 2 separate single flights and do not penalise you for mixing routes - therefore take full advantage of this with this tour.
Spend your first few nights in Trastevere apartment rentals and this will give you the full flexibility to really get out there and experience the city for yourself. Then the tour will start properly and you should definitely include Florence on your itinerary list as you head towards your next country.
Your next country is France, but only for a short time; this is because you are next heading to the tiny principality of Monaco. By all means book a couple of nights here and then head on to Marseille for a stay in the second city of France.
After this charming southern French city, it is then time to carry on west and head towards the Spanish border. Before you crossover though, first head up into the Pyrenees and visit the gorgeous mountain country of Andorra.
Once you have exhausted this idyllic area, then head into Spain and make the most of the eastern coast. There are numerous places to travel to here and most places are served by airlines that will offer you a good price on your return flight home.