Pale Walnut is one of those soft, warm off-whites with a putty undertone that Dulux Heritage does well — but you're paying a premium for the Heritage badge and its lovely flat matt. The good news is you don't have to.
The closest swap is Dulux Stone Sensation (LRV 59.7), which lands at just ΔE 1.1 from Pale Walnut — that's effectively imperceptible to the eye. It sits in the standard Dulux range, so you get the same colour for noticeably less money, plus you can pick it up almost anywhere and get it mixed on the spot. For a high-traffic hallway or kids' room, Dulux Diamond Matt in this shade will take a scrub without burnishing.
If you'd rather a slightly cleaner, brighter feel, Crown White Pepper (LRV 62.9) comes in at ΔE 1.6 — still very close, and that extra few points of LRV bounces a touch more light, handy in a north-facing room. Crown's trade matt is honest, hard-wearing and kind on the wallet.
My pick if you want something with a bit more character, though, is COAT Sweater Season (LRV 62.7) at ΔE 1.1 — same imperceptible match as Stone Sensation, but COAT's paint is genuinely lovely: low-VOC, water-based, and their flat matt has a chalky depth that punches above the price. It's also self-priming on most sound surfaces, which saves you a coat.
The "but what about" question: will a cheaper match look the same on the wall? At ΔE under 1.2, yes — the colour is the same. What differs is the finish quality and durability, not the hue. The Heritage line gives you a slightly deeper, more velvety matt; the alternatives are perfectly good but may read a hair flatter or need an extra coat on a tricky surface.
Practical advice: buy a tester of Stone Sensation or Sweater Season, paint two coats on lining paper, and move it round the room across the day before you commit. With warm putty tones, the undertone shifts a lot between morning and evening light.