Sorry to hear that you didn't get the mortgage LovelyHome...
Consolidation may not be possible, even in a year, so I wouldn't bank on it. If you take the CU loan, I'd look at it for the entire term and judge whether you can afford it on that basis, not on the basis of hoping you can consolidate to a lower rate in a year (or two) in the future. It may be possible, but I just wouldn't make any plans based on that.
I'd move into the house now, if it is indeed livable. You probably know this, but, if it's filthy, it's surprising how much difference a really good clean out & painting can do. If heat, water and light work, then you've got the basics. If you move into the house, you would save on rent and then do the granny flat up (with your extra income or your parents' loan (or a portion of the CU loan; you don't have to take the full 60k)). Then you could rent that out and get extra income to support another loan application. I know it would be hard to prioritise doing up the granny flat, rather than the main house but, if it can be a source of income, then that will help with both a new loan application and with general monthly income into the household.
€800 is a lot of money on rent - it would support a mortgage of (about) €200k at current rates, for example. Unless the house is verging on dangerous, I'd move in and see how it goes. Once you rent out the granny flat and you get a better loan rate based on that extra income, you could rent a separate place again for the period required to get the work done to the main house. It's all step-by-step, but I think that getting rid of that rent obligation is a priority.
Best of luck with it
Sprite