Typical current building costs are quoted at between €500 and €1000 per sq m, depending on your spec, access restrictions, ground conditions etc. On top of that you will have architect’s fees, planning / licence fees, site investigation costs etc etc, the total of which could come to 20% of the total build costs.
By spending the time now before you commit to get as many quotes as you have the time and patience to source you could save yourself a lot of € in the long run.
A good architect will save you his/her fees too in the long run if employed to do the leg work, oversee the works etc.
Always budget top end (unless you’re planning to do a lot of the work yourself or buy materials yourself or project manage yourself) and allow yourself a good contingency fund too!