If you want Wevet in a Dulux can, Sloe Flower is your colour. It comes in at LRV 81.4 with a measured ΔE of 0.7 from the original — anything under 1 is imperceptible, so side by side on a wall you genuinely wouldn't be able to tell them apart.
Clouded Pearl 4 is the other contender, and it's the same story: LRV 81.4, ΔE 0.7. The two Dulux colours sit so close together that picking between them is really a question of which is easier to get hold of. Both are dead-on.
Wevet is one of Farrow & Ball's cleanest, coolest off-whites — a soft white with a barely-there grey cast that stays crisp without tipping cold and clinical. It's a brilliant choice for north-facing rooms where you want light bounced around but don't want the flat sterility of a brilliant white. The fact that Dulux can land within 0.7 ΔE tells you the undertone is being faithfully reproduced, not just the lightness.
The "but what about" here is always finish and feel. A spectro match nails the colour, but it can't replicate Farrow & Ball's pigment density and the way their Estate Emulsion reads in changing light. If chalky depth matters to you in a feature space, pay for the real Wevet. If you're doing a hallway, a ceiling, or a rental where Dulux's price and durability win, Sloe Flower in Diamond Matt will give you a tougher, more wipeable finish for less money.
Practical tip: order a Dulux sample pot of Sloe Flower and paint two coats on a bit of lining paper, then move it round the room across the day. Cool off-whites are the most light-sensitive shades there are, and what looks perfect at 10am can drift grey by dusk. Test before you commit the whole room — that's the difference between a clean white and a cold one.