If you want to move from the Heritage range into standard Dulux — usually to save a few quid or because your local stockist mixes it more readily — Dulux Nordic Bliss is your colour. It comes in at ΔE 0 against Dulux Heritage Mallow White, which means there's no perceptible difference between the two. Same soft, barely-there warm white, LRV 80.9, just a different name and a cheaper tin.
Failing that, Dulux Cocoa Blush 6 is right on its heels at ΔE 0.5 (LRV 81). Anything under ΔE 2.5 is what I'd call a very close match, so at 0.5 you'd never spot it on a wall once it's dry and lived with for a day.
The usual "but what about" here: people assume Heritage colours must look noticeably more refined than the standard range. Honestly, for a near-white like Mallow White, that's a myth. The pigment recipe lands in the same place — the real difference between the two product lines is finish quality and the sheen options, not the colour itself. If you're painting walls in a matt emulsion, you'll get the same result from Nordic Bliss.
Where I'd still reach for the Heritage tin: if you want their flat matt or eggshell finish specifically, or you're matching trim and walls across the same range for consistency. The Heritage eggshell on woodwork is genuinely lovely and worth the premium.
A word of caution — match a tester pot before you commit a whole room. ΔE figures are measured in lab conditions, and your light, your existing skirting and the undercoat showing through all shift how a warm white reads. Mallow White and its matches will lean a touch creamy in north light and crisper in south-facing rooms. Get a brushout on the wall, live with it a day, then buy the big tins. Sorted.