Mole's Breath is one of F&B's most loved warm greys — a soft, mushroomy taupe-grey that shifts beautifully through the day. There isn't a dead-on dupe, but a couple of options get you close.
The nearest is Dulux Urban Obsession (LRV 21.6) at ΔE 3.3 from the original. That's not imperceptible — under ΔE 2.5 is what I'd call a proper match — but at 3.3 it's the same family and most people wouldn't clock the difference once it's on four walls. Crown Quarried Stone (LRV 26.6) is next at ΔE 3.6, though it sits noticeably lighter, so it'll feel a touch airier and less moody than the original.
Worth flagging: COAT Jojo's Green (LRV 25.9) comes up as a relative at ΔE 6.1, but that's a fair stretch — it leans greener and won't read as Mole's Breath in the room. I'd skip it if a faithful match is what you're after.
The "but what about" here is whether a budget match actually saves you anything. The honest answer: it depends what you're missing. Mole's Breath's magic is partly in F&B's pigment depth and the way Estate Emulsion handles light. Dulux and Crown are excellent paints in their own right — Crown's trade lines especially are a workhorse — but you won't get quite the same chalky depth. For a hallway, utility or a kid's room where you want the *look* without the spend, Urban Obsession is a sensible call.
Practical advice: buy a sample pot, paint a big A3 board, and live with it for a couple of days against your existing trim and flooring. Warm greys at this LRV swing hard depending on light — a north-facing room will pull them cooler and greyer than the chart suggests. If after testing the original still sings and the dupe falls flat, that's your answer: sometimes the F&B premium is buying you the exact mood you wanted.