Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
While BA Avios can provide very good value on European routes to/from the U.K., on an FCO-VCE-MUC-ATH-JTR itinerary, BA Avios would not be very useful. Neither BA nor its partners offers direct service between any of the city pairs on that itinerary.
The OP should check the cost of air (or train) travel between the city pairs on the itinerary, as well as the cost of hotel stays, and then decide whether it makes sense to use points/miles for flights or for hotel stays.