Simon, As there has not been an answer to your question.........yet.
I may be able to help.I'm no spanner man, but I'v owned just about every Fiat model(well almost).
There is a level check plug, and if you remove that, the oil should just be at that point.
If it does not leak oil, then it should not need touching for some time.
I have a Marea. @90k, and I have no need to change the oil , or top it up..
I owned a Lancia Beta 1400 in the late 70's(a Fiat Group product) and this car was front wheel drive and had a lovely little dip stick for the gearbox. For checking level and filling, but not these days unless the Idea is special in that respect.
Ian