If it were me, I would transfer the mortgage to an interest only National Irish Bank Mortgage. Your mortgage is very low and (assuming your house is valued at more than 150k) you will get a rate of 4% on your mortgage with NIB. However, you will also be receiving TRS on your interest payments which will bring the total interest paid to 3.2%. As the long term average of the stockmarket is somewhere around 11%, you should win hands down.
With this approach, your monthly mortgage payments will be reduced to a bit under €200. I would then put the entire 75k into a low cost fund (such as Quinn Life's) and also put the difference between your current monthly payments and the new monthly payment of €200 into the fund on a monthly basis.
Of course, using this method, your mortgage balance would remain at 74k. However, you could continue this approach whilst the value of your investment goes up (theoretically). Then, at any point, you could withdraw 74k from your fund to pay of the mortgage and should have a tidy amount left to continue investing or spend as you please.