check out the credit union website, it should list the current rates for various types of loan. I can't say whether it's the cheapest rate available but i do know that you will need to have a percentage of the loan you're looking for, in your account before being approved. They will also need to see regular deosits, so if you;re going to apply then start immediately, even if it's €50 a week.
as far as i'm aware the different CU's offer different ratios:
eg, CU No1 might require a one third 'deposit'
CU No2 might only require one sixth.
other institutions do not require 'deposits' to be held on the account for the term of the loan (eg banks). And there's a bit of paperwork (as you'd expect) for getting a loan.
I applied for a loan this year with a CU i'd been a member of for 20 years, and i had to reapply and then appeal the refusal i eventually got(after 3 weeks of getting extra quotes etc to them). A few days later they rang to say they'd made a mistake and of course i could have the loan. I politely refused and closed the account.