You are 60 and owe €1,000,000 on a house worth €450,000.
In general the reason that people don't over pay a tracker is that it's the cheapest money you will ever get. Better to save the surplus for changing the car, eduction what ever.
Not really sure that applies at 60. What's your goal here. Are you going to pay back the €1,000,000 over 15 years or just the €550,000 and sell.
If you can achieve a higher return on the surplus elsewhere then financially it make seance to invest it, if you want to live in a debt free house then pay down the loan faster.