Heating not available - Who bears the costs?

yes, could be. If you look closely, the heat pump should actually also be part of the electrical trade ;-)

I would simply try to have a conversation with the heating engineer and ask him if he can charge the regular price for the agreed room thermostats, but that you can obtain the ones for heating/cooling yourself.
The wiring effort is exactly the same. So he has no extra work.

The bimetallic dial thermometers are available for €40 each from a well-known German manufacturer.

why thermostat(s)? Especially with a Nibe with PC absolutely unnecessary. We have such a Nibe brine-water heat pump and installed "pro forma" exactly one thermostat per residential unit in the utility room (installed by an electrician, but also immediately deactivated again). Do a hydraulic balancing / set the flow rates properly once. Don’t forget the laws (especially the 2nd) of thermodynamics and then be happy. It has been running like this for us for a year and the tenants haven’t complained about a hot head or cold feet ;) The Nibe with PC cools automatically when it’s been hot outside long enough. The factory service for the initial start-up is quite expensive but also necessary for the warranty extension. The guys are good (for us anyway) and do it very sensibly (nonsense like legionella does not exist in a single-family house, heating element off etc.)

yes, could be. If you look at it closely, the heat pump actually also belongs to the electrical trade ;-)

I would simply try to talk to the heating engineer and ask him if he can charge the normal price for the agreed room thermostats, but that one can get the ones for heating/cooling oneself.
The wiring effort is exactly the same. So he has no extra effort.

The bimetal thermostats are available for 40€/piece from a well-known German manufacturer.

What interest should the heating engineer have in that? He now has his customer exactly where he needs him.
Either he agrees to the other heating with the expensive thermostats or he doesn’t get any heating and has to wait for the other...

Certainly, you can talk to the installer but you shouldn’t expect him to get involved in deals where he ends up even making a loss.
Because he still has to guarantee the installation... with devices he didn’t buy himself and from which he didn’t earn a cent...

PS:
You don't make money by being charitable as soon as the customer is in a situation where he would basically pay any price...

The heating installer also offers us to install only the heating without activating the PC or installing additional thermostats, etc. Basically for self-commissioning of the PC.

The heating engineer also offers to install just the heating without activating the PC or installing additional thermostats, etc. Basically for self-commissioning of the PC.

Then just book that and spend €500 on the factory customer service (but ask Nibe first if that's possible;-) But I don't fully understand, Passive Cooling is mEA automatic

What interest should the heating engineer have in that? He now has his customer exactly where he needs him? Either he agrees to the other heating system with the expensive thermostats or he simply won’t get a heating system and has to wait for the other one... Surely, one can talk to the installer, but one should not expect him to engage in deals where he ends up even losing money. Because he still has to guarantee the installation... with devices he didn’t buy himself and doesn’t earn a cent from... PS: You don’t make money by being charitable as soon as the customer is in a situation where he would basically pay any price...

I agree with you there. If the heating guy doesn’t go along with it because he assumes the guarantee for it, then he can argue it that way. But he could also exclude the room thermostats from the warranty if that’s what matters to him. He wouldn’t make a loss either if he bills ERR but doesn’t deliver. On the contrary... I don’t understand why “additional” thermostats are being talked about here when it comes to the cooling function. I don’t see a five-figure additional amount for that either. Your last argument sounds more like a boxing ring, just before throwing a knockout punch. I always think it should be fair on the construction site and, given the current supply and price situations, compromises from both sides can sometimes be expected.