If you love Dimpse but don't fancy the Farrow & Ball price tag, Dulux Glacial Flow is your answer. It comes in at a ΔE of 0 against Dimpse — that's a textbook colour match, genuinely imperceptible to the human eye. You'd struggle to tell two drying-down patches apart on the same wall.
Dimpse is that lovely soft grey with a whisper of blue — the colour that sits between the warm greys and the cool ones, reading calm without going clinical. Glacial Flow (LRV 65.7) carries that same gentle, airy quality. At that LRV it stays light and reflective, so it's a cracking choice for north-facing rooms, hallways and anywhere you want a restful grey that won't tip too cold.
Your second option is Dulux Polished Pebble (LRV 68.6), which lands at ΔE 1.1 from Dimpse — still very close, just a few points lighter. If your room is a bit gloomy and you want to claw back a little brightness, Polished Pebble is the one to grab. In a bright south-facing space, though, stick with Glacial Flow for the truer match.
Now, the honest caveat: a ΔE match gets you the colour bang on, but it won't give you the *finish*. Farrow & Ball's Estate Emulsion has that famously chalky, light-absorbing depth that Dulux's standard emulsions don't quite replicate — Dulux tends to read flatter and a touch more plasticky in the same light. For most living rooms and bedrooms you'll never notice; in a feature room where you want that F&B chalkiness, it matters.
My advice: order a sample pot of Glacial Flow, paint a decent A2-sized patch (two coats), and live with it across a full day before you commit. Match the sheen level you'd actually use — don't judge a matt scheme off a satin tester. Get that right and you've saved yourself a tidy sum with no compromise on the colour.