Brendan, pretty much on the same page in terms of a house in the 400k price range, though differ on the 'intermediate' view. Few edits, clarifications:
This is an interesting way of looking at it. She has savings of €45k and negative equity of €75k, so her current funds are -€30k.
Not literally deposit less NE, though understand my phrase led you there. I meant their then current or available funds/resources. They have an available deposit of 45k now and a current ability to save. In 5-10 years if they rent I can't see how they will get near having a sufficient deposit. Also run the significant risk that house prices could run ahead of their ability to save??
If she goes for a €400k house, her position will be a house worth €400k with a mortgage of €430k or €30k negative equity. It will be some years before they can trade up. They will have to pay down the NE and build up equity of at least €100k. So "intermediate" looks like at least 5 years, and probably, 10 years.
This is really critical, as given their likely ages, salary profile, living costs, children, etc, I can't see how they could pay off NE of 76 and save another 50. That's over a thousand a month for 10 years (or 2,000 per month for 5). Simply not do'able based on the facts here.
So "intermediate" looks like at least 5 years, and probably, 10 years.
It may simply be the term 'intermediate' house. To me that suggests another interim and suboptimal solution, with the clear expectation that they move again. My caution/concern is that if they go into the situation with this mindset, they could end up with a house they are not really happy with and always are looking towards the next move. That next move could really be difficult. My suggestion is to rethink the type of house that is acceptable to them longer term (20 year time frame) and seek that house now, though it needs to be in the region of 400k.
It may be that at a future date finances and circumstances allow a trading up. However, I would not, if I was them, go buy a house and look at it as an intermediate solution.