Cornforth White is one of those clever F&B greys that does its best work staying out of the way. It's a backdrop colour — the wall against which everything else gets read — so the trick is letting it sit quietly and putting your interest in the accents.
Start with the woodwork. Don't reach for a pure brilliant white, because next to Cornforth it reads dead and slightly grubby. A slightly warmer white like Wimborne White keeps the trim crisp without that cold clash. That alone sorts most of the rooms I see going wrong.
For accents, go cool, not earthy. Cornforth has a faint pink-grey undertone, and warm terracottas, ochres and muddy greens drag that pinkness out where it looks uncomfortable. Instead, lean into cool mid-greys and soft inky blues. Paint & Paper Library's Blue Blood (LRV 16.4) is a cracking choice for a feature wall, a chimney breast, or joinery in an adjoining room — deep, cool and confident against the pale grey. For something even moodier on a study door or alcove, Mylands Cigar BH.20 (LRV 11.8) gives you that rich enveloping contrast.
If you want a lift rather than a drama, a gentle wash of green works beautifully — Dulux Almost Pistachio (LRV 80.3) is barely-there and soft, ideal for a ceiling, a hallway leading off, or as a fresh counterpoint in a kitchen.
The "but what about a warm scheme?" question comes up a lot. Honestly, if you want a warm, cosy palette, Cornforth isn't your starting point — Skimming Stone or Ammonite play far nicer with warm tones. Cornforth wants cool company.
Practical bit: always test it on at least two walls and look at it morning and evening. In a north-facing room Cornforth can go properly grey and a touch cold, so check it's reading the way you want before you commit the whole room.