[stoppingdown]

Yes, my screen is calibrated. I understand that most consistent results might be achieved with sRGB, but I find this is unacceptable: any serious printing service must properly work with AdobeRGB (at a minimum: for professionals I'd expect wider profiles should be supported).

In any case, the first printing service mandates that you submit photos with the specific profile they provide for each kind of paper, so I just followed their instructions.

In the meantime samples arrived from a second photo service. Just a tad better, but still unacceptable. It's quite clear that I need to manually correct something (for instance they publish with warmer tones); to tell the truth I expected that I had something to manually correct for what concerns the overall luminosity, for the obvious reason that it greatly depends on the conditions in which you look at printed paper.
The problem now is how to apply corrections in batch mode, as I don't think Capture One supports this feature (I remember that Lightroom did).