If i was me i would approach the seller/builder with your plans, if it's a builder selling he would probably be happy to get the sale at €200k and then have the chance to get the additional work (at an agreed price) as apposed to someone else doing it. Im sure this would not have worked a couple of years ago when they didnt want to bargain at all, it was common that they didnt even bother to fix snags properly.
Is the house a turn key finish? If not you should discuss getting the seller to provide Kinished kitchen, fireplace, coving, tiling stc.. to your choosing as they would be able to purchase the goods less the vat and this could all be included in your mortgage.