Sorted — you don't need to pay Heritage prices for this one. The standout is Crown Craft Fair (LRV 39.6), which lands at ΔE 1.2 from Dulux Heritage Sage Green. Anything under 2.5 is what we'd call very close, and 1.2 is the kind of difference you'd only spot with both samples side by side under a lab light. On a finished wall, nobody's clocking the difference. Crown sits a notch below Dulux Heritage on price and the trade availability is excellent, so it's the one I'd reach for.
If you want to go cheaper still, Dulux Woodland Pearl 3 (LRV 42.2) comes in at ΔE 3. That's just outside the "very close" band — slightly lighter and a touch greener — but in standard Dulux it's the most wallet-friendly route and perfectly fine if you're doing a big space or a rental. It'll read as the same colour family; the nuance only shows when you're being fussy.
Worth flagging the one that *isn't* a match: COAT Hamilton (LRV 48.1) sits at ΔE 6.1, which is a noticeably different, lighter, fresher green. Lovely colour in its own right, but don't buy it expecting Sage Green — you'll be disappointed.
The usual caveat: a close ΔE matches the colour, not the finish. Dulux Heritage has its own velvety matt with a slightly chalky depth, so if that surface quality is what drew you to it, a Crown or standard Dulux equivalent will read a fraction flatter. For a sage green at this depth (LRV under 40), that's rarely a dealbreaker.
My advice: order a Craft Fair sample, paint two coats on lining paper, and prop it against the wall morning and evening before you commit. Greens shift hard with the light, and a north-facing room will pull this one cooler and greyer than a sunny one.