You can take 25% of your pension as a lump sum when you retire. The first 200k of the lump sum is tax free and the next 300k is taxed at 20% and the rest is taxed at 40%. If your pension fund is worth less than 800k when you retire, all of your lump sum will be tax free.
So if you contribute €1000 to your pension now and get 20% tax relief on the way in, the net cost to you will be €800. When you go to withdraw that €1000 from your pension in future, you will take €250 tax free and pay 20% on the other €750 which is €150 in tax. So you will net €850 from your pension.
But the biggest advantage is that your €1000 will grow without any tax being deducted until you withdraw it from your fund. Depending on what fund you invest in, and over how long, this could be very significant.
After clearing any debts and your mortgage, I think that pension contributions with tax relief, even at 20%, are the next thing I would be considering.