Mylands makes a cracking paint, but Holland Park No.5 doesn't come cheap, and if you're doing a whole room — or worse, a whole house — the cost adds up fast. The good news is there are genuinely close matches across the board.
COAT Pablo is the standout for accuracy. At ΔE 0.5 it's the nearest of the three, with an LRV of 82.6 — virtually indistinguishable from the original, which sits in the same soft off-white territory. COAT's a strong eco-credentialled brand and works out cheaper than Mylands, so if you want the colour spot-on without the premium, that's your pick.
If you'd rather grab a tin from a trade counter, Dulux Vanilla Mist 1 is the value play. At ΔE 0.6 it's effectively a dead match (anything under 1 is imperceptible to the eye), with an LRV of 80.8 — a touch deeper than Pablo but you'd never spot it on a wall. Dulux Trade emulsion is widely stocked, easy to get colour-matched, and the cheapest option here per litre.
Crown Sail White rounds it out at ΔE 0.7, LRV 83.3 — the brightest of the three, so it'll bounce a little more light around a darker room.
The honest caveat: Mylands paint has a particular depth and chalky finish that's part of what you're paying for. A ΔE under 1 means the *colour* is matched, but the feel of the film and the way it handles light can differ slightly between brands. For an off-white this rarely matters — the differences only really show on deep, saturated colours.
My advice: order tester pots of Pablo and Vanilla Mist 1, paint two coats on lining paper, and view them in your actual room morning and evening before committing. On an off-white like this you'll almost certainly be happy with the cheaper tin.