Where to start! Firstly, I think that your other half has a little bit of a spending problem. They aren't paying towards the mortgage so basically they are living rent-free on an income of 55k and they can't keep in it? By the looks of what you have listed below, you pay for holidays too. That is a bit unreal, what are they spending it on!!? By my calculations (based on what you have listed below), your list amounts to €3140.59 and your OH's list amounts to €1014.65
including car-related expenses that you are forking out for. Excluding those, by that list they have monthly outgoings of €887.48!!! SO the question is.... what are they spending the money on? I know I am repeating myself here but there does seem to be a pretty sizeable chunk of cash going astray somewhere in that. From your list your OH is only contributing €200pm to household expenses (€500 if you include the car. I am excluding the CU loan as evidently that is something they took out alone so am assuming it was for their benefit rather than yours collectively), so in effect you are operating as a single income household, i.e. yours plus a little bit extra.
They may not want to discuss it but this is a serious issue. They are beyond their means and they are putting both of your financial well-being in jeopardy. Both of you need to start HONESTLY recording a spending diary and to account mutually for your expenditure at the end of the month. It may cause rows, in fact it probably will but (and I am being blunt here) if they cannot account for their incomings and outgoings they are taking the proverbial. It is disrespectful to you to treat you as a free money bank and just abuse your income to shore up extravagance. Starting to sound a little outraged now
Has this been an ongoing issue? Or did it suddenly become a problem? Have they given any explanation for the shortfall? I am not asking you to answer these questions in public but I think you need to consider them in private at least. Potentially there is something your other half is concealing from you that might be detrimental to one or both of you. Money issues is frequently cited as one of the root causes of broken or strained relationships (in the UK at least) so the sooner you get to the bottom of this the better for you both.
On your side the only thing I can note is that you seem to be spending an awful lot of money on public transport. If this is your commuting cost, look into the
taxsaver scheme immediately (assuming you are not self-employed, in which case is it a business expense?).
Seems I was a bit slow - I will leave the post as it is but I notice you have answered some of my points already