Tea with Florence is one of Little Greene's loveliest greeny-teals — that soft, slightly dusty turquoise that reads green in some lights and blue in others. Dulux doesn't have a perfect twin for it, but two come close enough to consider.
Your best bet is Dulux Teal Voyage, at LRV 20 with a ΔE of 3.5 from the original. That's a reasonable match — close in both depth and hue, though at a ΔE above 2.5 you'll spot a difference if you hold the two swatches side by side. Teal Voyage tends to lean very slightly cooler and bluer than Tea with Florence.
Second in line is Dulux Neptune Seas, LRV 17.1, ΔE 3.7. It's marginally darker and a touch more saturated, so it'll feel a bit moodier on a wall. Pick this one if you actually want a deeper, more dramatic version rather than a true like-for-like.
Here's the honest bit, though. Once you're past ΔE 2.5, you're no longer matching — you're substituting. Tea with Florence has a particular soft, chalky quality that comes from Little Greene's pigment load and their flat finishes. Dulux in a standard emulsion won't replicate that depth of character, however close the hue figure. If it's a small job, the saving isn't worth it.
Where a Dulux match genuinely earns its keep is durability. If this teal is going somewhere that takes a hammering — a hallway, a kitchen, kids' bedroom — Dulux's Diamond Matt or washable lines will outlast Little Greene's flat emulsion for scuffs and wiping. That's a sensible trade.
My advice: order sample pots of Teal Voyage and Tea with Florence both, paint them on the same board, and live with them through a day of changing light before you commit. Teal especially shifts a lot between morning and dusk, and the photo on a website won't tell you which way yours will go.