+1 on the relays!
The other thing it could be is what mine suffered from a couple of years ago...
Driving along the A2, then suddenly nothing (other than ignition lights!)
Engine would turn over, but not fire up.
I found that a brown fuse (7.5A I think) had blown - it's one of 3 or 4 fuses mounted above the main bank of fuses by the drivers right knee... easy to miss, you have to get your head down in front of the drivers seat and look up into the fuse compartment to see them.
Long story short, it turned out to be the key code / immobiliser module that failed (small black box with a green sticker on, mounted under the dash, near the steering column).
My car ended up having to go to the local Fiat garage where a new module was ordered, installed and programmed.
Total cost, IIRC, was about £230.
"Looking through the knothole in Granny's wooden leg"