Loft White is one of Little Greene's cooler whites, and the trick is to lean into that rather than fight it. There's a faint green-grey in it that stops it going clinical, so you want everything around it to sit on the cool side of the line. Warm it up with creamy taupes and it'll look muddy and confused — keep the whole envelope cool and it sings.
For a soft architectural pairing, Paint & Paper Library's Slate IV (LRV 67.5) is a lovely match. It's a light, gentle grey that picks up the same cool undertone as Loft White, so the two read as part of the same family. Use Loft White on the walls and Slate IV on a chimney breast or alcoves, or flip it for a slightly weightier scheme.
Want a bit more depth? Mylands Artichoke BH.13 (LRV 27.6) brings in that washed green-grey direction without going full sage. It's a cracking mid-tone for joinery, a kitchen island, or a panelled section of wall — and because it echoes the green hiding in Loft White, the pairing feels deliberate rather than accidental.
For proper contrast and drama, go deep with Dulux Sapphire Springs 1 (LRV 6.4). That's a near-inky cool blue, brilliant for a feature wall, a front door, or window reveals where you want Loft White to read as crisp and bright against it.
The one thing I'd steer you away from is warm metals. Brass and aged gold will clash with the cool cast. Reach for brushed nickel, chrome or matt black on handles, taps and light fittings instead — and architectural black for window frames or skirting if you want a sharper edge.
Practical tip: paint big test patches and view them in your actual light. North-facing rooms will pull the green-grey forward, which can be gorgeous but worth checking before you commit a whole room.