If you want Little Greene's Sage Green in a Dulux tin, go for Jungle Fever 1. It lands at ΔE 1.8 from the original, which is a very close match — most people won't clock the difference once it's on the wall and dry. Its LRV is 21.1, so it's a properly grounded, mid-depth green that reads soft and dusty rather than bright.
The runner-up is English Mist 1 at ΔE 3.2 (LRV 18.8). That figure is past the "very close" threshold of 2.5, so it's a *visible* shift — slightly deeper and a touch greyer side-by-side. Fine if you like it as its own colour, but don't kid yourself it's a dead ringer for Sage Green. Jungle Fever 1 is the one to ask for at the mixing desk.
A word on why you'd even bother matching: Little Greene's pigment load and the way their colours shift in changing light is part of what you pay for. A Dulux match gets you the *hue* very accurately, but it won't have quite the same chalky depth or that subtle movement through the day. If budget's the driver, the match is a sensible call. If the room's a showpiece and you love the original, I'd spend the extra and buy the Little Greene.
Whatever you land on, always brush out a test patch and live with it for a couple of days — north light will pull this green cooler and greyer, while a warm south-facing room will lift it and bring out more of the yellow-green. Paint two coats on lining paper or an offcut and move it round the walls before you commit a whole room to a tin. Get that sorted and you'll have no surprises.