I don't know if the spots are dimmable.
I don’t know the exact situation but I think the costs are definitely too high!! It was only a suggestion! And why a socket? The dimmer replaces the light switch, unless you have a double one for the mentioned mirror.
I had the situation in the living room, a double switch, so the socket had to give way – because the dimmer takes up a whole “space.” In the bathroom it is also a double switch (the other for the mirror), ergo...
As for the costs, mea culpa, indeed TWO dimmers cost €350 (280+VAT, and just the material), so sorry, €175 then... that is the amount shown on the electrician’s invoice, who replaced the double switch and the socket in the living room with two dimmers. Plus labor.