Pro of a CU loan is you can pay more than you like to an unlimited amount. For example, i am lead to believe that with traditional banks, you only can pay back an agreed set amount over the actual repayments.
With the CU I can wander down tomorrow and pay 10k off the loan and they won't bat an eyelid. So if you're in a position to that early on, then going with the CU is a good idea. You can always look at switching it over to a 'normal' bank once you think you're gonna start repaying normally. but if you can get ahead on the loan from the word 'go', then you can knock years off the term with a bit of effort.
There are rules, the gist of it in Drogheda is that you can only borrow up to 100k. You have to have a minimum of 5% of the value of the loan in your savings, the loan is secured against the house with the CU getting a first legal charge on the property, etc.
It's called a Home Improvement Loan, as, as has been said, the CU aren't really allowed to do actual mortgages (unless that's changed in the mean time).