Thanks callybags. Yes - it's just fuel. Company pays for servicing, tyres, etc.
They use a software package for claiming expenses, so the journey is entered, mileage automatically calculated (via google maps or similar) and the company rate applied, so if I do a 100km journey it will calculate my expenses as €13 (based on the current 13c per km rate). You're right in that the car will advise the L/100km figure, but I don't have the option to amend unfortunately.
Ideally, if there was a similar advisory rate here like there is in the UK it would make it much easier, as the UK rate has crept up over the last 12-18 months to reflect higher fuel rates.
Appreciate your response.