Hi beer,
Based on the details you gave (26,000) outstanding, 3.5 years left and 4.1 % interest I estimate you pay just under 700 euro a month not including insurance.
So I’d recommend you pay it in full and use the monthly savings to replenish the cash. Think of it this way - in order to get a return on the cash you have you’d need to be getting a return of 8 % per annum when you take DIRT and other taxes into account.
Unless you need the cash for something else, I’d pay it off in full. If you prefer save maybe 3 months net salary (6,000) and pay the balance off the mortgage.
To be honest though I’d pay it off in full given the details you’ve supplied here.
Best,
Opus 2018