I'm in the process of transferring the deeds to the house bought with my partner into my sole name. I would be in a position to put another 10K into the mortgage but am not sure if should do that or rather go to a broker and invest it somewhere.
My mortgage is for 236.000K taken out this year and running for 30 years.
30 years is a long time... have you considered the interest savings to be made were you to use the €10K to reduce your term? Crunch the numbers with Karl Jeacle's mortgage calculator.