Right, let's be honest up front: paint alone won't stop mould. Mould grows because warm, damp air condenses on a cold ceiling and lingers. If you don't fix the ventilation, even the best paint will eventually let you down. So sort the extractor fan, crack a window after showers, and keep the door shut — then choose the right paint.
For the topcoat, go with a dedicated bathroom emulsion that has moisture and mould resistance built in. Dulux Easycare Bathroom is the reliable workhorse here — it's a soft sheen that shrugs off steam and wipes clean. Crown Easyclean Kitchen & Bathroom is just as good and has a lovely tough finish. Both contain fungicide in the film, which slows mould taking hold on the paint surface itself. A soft sheen or mid-sheen is the move on a bathroom ceiling, not a dead-flat matt — sheen sheds moisture far better than a porous matt finish, which is exactly where mould loves to settle.
If you've already got mould up there, don't just paint over it. Kill it first with a proper fungicidal wash, let it dry fully, and if there's any staining bleeding through, hit it with Zinsser Cover Stain or BIN as a stain-blocking primer. Paint straight over an old mould stain and it'll grin back at you within weeks.
The "but what about my fancy F&B ceiling" question: I love a heritage matt, but a north-facing bathroom that steams up daily is no place for a chalky flat emulsion — it'll go patchy and grow black spots. Save the Farrow & Ball matt estate emulsion for the bedroom.
Colour-wise, keep ceilings bright and clean to bounce what little light a bathroom usually gets — Dulux White or a soft off-white reads fresh and makes the room feel taller. Practical advice: two coats, ventilate while you paint, and replace a feeble extractor fan before you blame the paint.