Borrowed Light is a soft, sky-washed blue with a cool undertone, and the cardinal rule with it is simple: keep the company cool. Warm it up and it goes muddy and a bit sad.
Start with the woodwork, because that's where people most often trip up. Keep it clean rather than creamy — Farrow & Ball All White (LRV 92) is the natural partner here, a neutral, pure white with nothing yellowy about it. Strong White or Wevet do the same job with a cooler cast. What you must avoid is anything creamy: Wimborne White or a softened off-white will read dingy against that crisp blue and drag the whole scheme down.
For the rest of the room, build interest through texture and tone rather than contrast. A pale stone like Paint & Paper Library Sand I (LRV 95.4) brings a bright, barely-there warmth that lifts Borrowed Light without arguing with it — think cool linen, plaster, pale oak. It keeps things calm and luminous, which is exactly what this colour wants to do.
When you do want a moment of depth, reach for muted, grounded tones. Mylands Cigar BH.20 (LRV 11.8) is a deep, warm tobacco brown that anchors the palette beautifully on a piece of joinery, a chimney breast or a single door — used sparingly. For a touch of warmth in accessories only — a cushion, a lamp base, a framed print — Dulux Copper Glow (LRV 30.1) gives that flash of muted terracotta-copper that stops the scheme feeling clinical. Use it on textiles, not walls, and never as a metallic finish.
The "but what about" question I always get: can I do brass and warm gold fittings? Honestly, not with this one. Warm metallics clash. Stick to brushed steel, chrome or matt black ironmongery and the room will hang together.
Practical tip: paint a board and look at it both ends of the day. Borrowed Light is gorgeous in good north or east light but can flatten in dim rooms — if yours is gloomy, lean harder on the pale stone to keep things bright.