Honest answer, mate: nothing in the cheaper brands gets you a clean swap for Little Greene Hicks' Blue. It's a deep, muted slate blue — grey-softened rather than bright, sitting at LRV 10 — and the nearest matches we've measured all drift off enough to read as a different colour on the wall.
The closest is Crown Midnight Navy (LRV 6.6) at ΔE 5.9 from the original. To put that in context — anything under ΔE 2.5 is what we'd call very close, under 1 is imperceptible, and past 4 you're into "related but different colour" territory. At 5.9, Midnight Navy sits in the same smoky-blue family but reads visibly darker and more navy, so treat it as a neighbour, not a twin.
The other contenders are further still: Dulux Azure Fusion 1 (LRV 5.4) lands at ΔE 9.6, and COAT David Rose (LRV 4.1) at ΔE 12.6. Both are darker and more saturated than Hicks' Blue — useful colours in their own right, but not stand-ins for this one.
So here's my steer. If you genuinely love Hicks' Blue specifically — that soft, slatey, grey-tempered quality — buy the Little Greene tin and be done with it. On a feature wall or a few metres of joinery the price difference is small in real terms, and you won't spend the next two years squinting at a near-miss wishing you'd just bought the original.
If the budget is firm and you're open to *a* good deep blue rather than *this* blue, Crown Midnight Navy is the one I'd look at — the closest of the bunch, solid trade-friendly paint, and a sensible price. Just go in knowing it's its own colour, not a dupe.
Whatever you land on, order a sample pot and brush out a test patch, then live with it across a full day. Deep blues shift hard between grey morning light and warm evening light, and that swing matters far more than a few quid on the tin.