House price okay? KFW 55, 190 sqm, without basement

We have now received the updated offer for 243,150 €. Surcharges for clinker, roller shutters, and windows leave a remaining amount of 4,200 €. This makes the cement-based plaster about 1,000 € more expensive than expected (we were told a surcharge of 6 € per m² - but according to my calculations, it is now 10 € per m²) - should we address this with the BU?

The BU has corrected the price again on its own. Now I have a question about the connections for water and electricity (and construction water/construction electricity): are these fixed prices according to a statute or is it free market?

For this, you need to contact the responsible provider and have them make you offers. This can vary by region.

That's exactly what we did and now have the offers - it was only a question of whether the prices are fixed then, or if it might be possible to get it cheaper somehow. But your statement sounds as if it is fixed (per region).

These are fixed prices, unless the supplier allows another company to carry out the work.
In our experience, a company authorized to do so is more expensive than the supplier itself.

We were allowed to have various works performed by our civil engineer. The material was provided by the supplier.
For us, these were the piping of the water and gas lines. Afterwards, the supplier only had to push through the final gas line and set various shut-off valves.
In addition, the supplier laid all connections into the house and installed the meters.