If you want Pale Walnut but would rather buy from Dulux's standard range — usually cheaper and easier to get mixed at trade counters — Stone Sensation is your answer. It lands at ΔE 1.1 from Dulux Heritage Pale Walnut, which is imperceptible to the eye. Anything under ΔE 1 is a textbook match; 1.1 means you'd never spot the difference once it's dry on the wall.
The close runner-up is Dulux Timeless at ΔE 1.2 — also a cracking match, and one of the most-used neutrals in the country for a reason. Both sit in that warm, soft, just-off-white territory: Stone Sensation reads at LRV 59.7 and Timeless at 61.7, so Timeless will bounce back a touch more light. In a darker, north-facing room that extra brightness can be welcome; in a south-facing room flooded with sun, Stone Sensation's slightly lower LRV keeps things grounded and stops it tipping too pale.
The "but what about" here: people assume the Heritage line is just standard Dulux with a posh label. It isn't — the Heritage range uses a different base and tends to have a denser, flatter finish with better depth, especially in the matt. So while Stone Sensation matches the colour almost perfectly, the Heritage Pale Walnut will look a hair richer in certain lights because of how the paint film behaves, not the pigment. For most jobs that's a non-issue.
Practical advice: order testers of both Stone Sensation and Timeless, brush two coats onto A4 lining paper, and prop them against the wall at different times of day before committing. Match figures get you 95% of the way there — your own light does the last 5%. If budget's the driver and you just want Pale Walnut on a wall, go Stone Sensation and don't look back.