Building law: Electrician refuses to continue

but you were informed about additional costs every time @hampshire, right? Whether you then request a new offer or not is another matter

You were informed about the standard price. You exceed it with your wishes. You could have requested an offer. But in practice, this leads to a house construction taking not 9 months, but 2 years. That is why theory and practice differ greatly in construction. In our last build, we completed many trades on verbal agreement – verbal agreement on prices and verbal acceptance of the offer. The same applies to change requests. Sometimes the craftsman said approximately what it might cost, sometimes there was an invoice later. If the electrician is on site and drills a few additional sockets, I cannot wait for a written offer. Do it or leave it. As I said, this is a learning experience for you. But it has happened exactly as it does daily on thousands of construction sites.

Did you necessarily want the pattern specifications and significant changes, or did you just keep ordering merrily as long as no supplementary offer came, in the naive hope that everything would then be included?

If the former, then it's obviously necessary to possibly have the additional services itemized again and then pay for them.
If the latter, it was a bit naive.

Asked the other way around. What exactly is your main problem? That it costs more at all, or that it is that much?

Did you definitely want the pattern repetitions and significant changes, or did you just keep ordering happily as long as no additional offer came in, in the naive hope that everything would then be included? If the former, then it is clear to have the additional services possibly itemized again and then pay for them. If the latter, it was a bit naive.

It was actually the latter. The electrician also explicitly pointed out things to us that are standard nowadays and that we should definitely install sockets for the Christmas lights in the window reveals. He never said anything about the costs and I never even thought of asking about extra costs, as I always assumed high-quality electrical engineering and the developer conveyed the standard service description as the cost estimate, even when the floor plan was not yet final.

Let me ask it the other way around. What exactly is your main problem? That it costs more at all or that it costs so much?

That I could have consciously decided to pay the extra costs if I had known about it.
Then I wouldn't have 12 sockets in the pantry and 9 in the wardrobe now.

I didn't even come up with the idea of asking for additional costs, as I always assumed high-quality electrical engineering and the developer conveyed the standard construction service description as the estimate, even though the floor plan was not yet final.

And in addition to my question, is the standard construction service description part of the contract?