€90/week = €4,680 p.a, suggests you have a 5-year loan and are therefore repaying a total of about €23K for that €15K. As RainyDay says, it sounds like it's a fixed rate loan. But in any case, ask them
(a) what the outstanding balance is, and what fees you'd incur by clearing this,
(b) what rate you're on, exactly
(c) what replacement loan/refinancing structure they could propose, and on what terms (fixed or variable, etc.)
Compare (b) and (c), compare (c) to the other options available to you (see the Best Buys sticky) — and then see how all that compares to the option of just continuing to pay down the existing loan as per the agreed schedule. You probably don't have
the most competitive rate on the market on that loan, but it's not a huge amount and if it costs too much in penalties to redeem it and start afresh, it may not be worth it — especially as rates have now started to rise from the all-time low they were at when you presumably fixed the loan, 16 months ago.
I would like to think if we had a financial crisis we had a bit of leeway.
If you're tucking €100+/week away in the CU, you're both building up an 'emergency fund' and saving towards a deposit. What rate are you getting from the CU?