District One mansion, a few things in the finishing are not right after handover, how do I get a premium builder to sort them?

You're right not to accept it, at this level the standard should be exact, and finishing snags on a big bespoke mansion are common precisely because there's so much handcrafted stone, joinery and plaster for something to move or be imperfect. The leverage is the same as any handover but you hold it to a higher bar: document every issue with photos, location and a note, and raise it formally within the defects liability period so it's the builder's obligation to fix at no cost, stone or marble lippage and hollow tiles, joinery that's dropped or opened, paint and plaster imperfections, and any alignment that's off. The difference with premium work is the FIX has to match the original, colour, grain, stone and profile matched, not a visible patch, so you want a finishing team that can restore to that standard rather than just fill and repaint. So it's thorough documentation inside the defects window, insistence on match-quality repairs, and, if the builder drags, an independent finishing snag report gives your list professional weight. A team that does high-end finishing works in District One mansions will know what a mansion-grade finish should look like and can either drive the snagging or do the match-quality repairs. Log it all now, while the defects period is your leverage.