If you want Night Fishing's deep plummy-purple in a Dulux can, go for Dulux Amethyst Falls 1. It lands at ΔE 1.9 from the original (LRV 5.8), which is well inside the "very close" band — most eyes won't pick it apart from Sanderson's version on the wall.
Your back-up is Dulux Plum Compote at ΔE 2.4 (LRV 5.9). Still a tidy match, just a touch further off — it leans very slightly different in undertone, so I'd treat it as the second choice rather than a dead heat. Both sit around LRV 6, so you're working with a properly moody, light-swallowing colour either way. That's no bad thing for the kind of room this shade suits — a snug, a bedroom, a panelled dining room — but it does mean you'll want the lighting sorted before you commit.
Here's the honest bit, mate: a ΔE under 2.5 is a genuinely good match, but a colour this dark is *all* about undertone, and undertone shifts under different light and on different sheens. North light will pull the purple cooler and bluer; warm artificial light at night will push it richer and more wine-coloured. So don't take my word or the numbers alone — get a tester of Amethyst Falls 1, paint two coats onto an A4 of lining paper, and live with it on the actual wall across a full day and an evening.
Why switch to Dulux at all? Usually it's availability, price, or matching into an existing Dulux spec on a job. If you're not tied to it, Sanderson's own Night Fishing is the truest version and worth pricing up first. But if Dulux is the brief, Amethyst Falls 1 is the one I'd order.
Use Dulux Diamond Matt or their eggshell for a dark colour like this — the tougher finish wipes clean, which matters more on deep shades that show every scuff.