Had a similar problem, tho thankfully not the flat battery.
1) check the year of the car against the year of the stereo - those cunning fiat engineers decided to alter the electrics between the mk2 and the mk2.5, the power leads alter pins, so you might well find that there is a permenant drain to earth. Very easy to fix on the plus side, just check the wiring diagram between the two units and switch over the needed wires.
2) The sat nav needs to be installed. This is because although it has a gps signal it doesn't know where that is in relation to the map. (if the attachment works have inlcuded the manual for the stereo - should help with the install!!)
3) I suspect that if it didn't have sat nav orginally it won't have the garla lead (speed signal pulse lead) which is what the unit will need, without it the unit won't install- trust me i have tried it several times and sworn at the thing. Hence you will be stuck with it not knowing where it is. (at the moment i have this problem and have no idea how to fix it) I am aware you can retro fit units which magnetise the steel bands on your tyre and use that to generate a signal pulse- but they are +£80 and are rather tacky. so i don't know if anybody has any ideas how to get round it? (other than replacing the electrical wiring harness!!!)
If it helps you are not alone i think a lot of people are suffering this problem!
