I'm afraid this is the way it works. You will be stuck with this rate for a whole year. You have two options:

  1. Talk to your bank and ask for your mortgage to be revised every 3 months (probaby useless, as banks are seldom helpful)
  2. Take your mortgage somewhere else (provided you find a bank willing to offer you better conditions, which might be not that easy at the moment). Not only you will be reducing your 1.25% margin rate, but also the Euribor will be that of the month the binding offer is issued. This has a cost of 0.5% subrogation fee, plus around an extra 0.5% for notary an registry fees, and lawyers fees of 0.5% (in total 1.5%). At the current rates, you would be paying around 3% less on the principal on your first year (1.5% after costs). On a mortgage of, say, €300,000, the savings would be of €4,500. The worst that can happen is that, upon receiving the binding offer, your current bank matches it to prevent you (by law) from leaving.
Marta (our mortgage expert) may be able to offer further advice.