If you want a Dulux stand-in for Mylands Bond Street No.219, go for Dulux Raven Plume. It comes in at ΔE 2.3 from the original, which is a very close match — close enough that on a finished wall, in normal light, you'd struggle to tell them apart.
Bond Street is one of Mylands' deep, near-black charcoals with real depth to it, and Raven Plume (LRV 8.4) captures that moody softness rather than reading as a flat, dead black. That low LRV means it'll behave like a black in most rooms — it'll swallow light and feel enveloping, so it earns its keep in a hallway, a study, or as joinery against a paler wall.
Your second option is Dulux Basically Black at ΔE 2.5 (LRV 7.3). Still a very close match, just a touch deeper and very slightly off from the original. If anything it leans a hair blacker and cooler than Raven Plume, so it's the one to reach for if you want maximum drama and don't mind losing a sliver of the subtle warmth in the Mylands.
Now — the honest bit. Mylands paint has a particular density and sheen quality, especially in their Marble Matt, that Dulux won't perfectly replicate even with a spot-on colour match. You're matching the colour, not the finish. If the look of Mylands is what you're after, the paint film itself contributes to that. A ΔE under 2.5 sorts the colour; it won't give you the same body underfoot.
My advice: get both Raven Plume and Basically Black brushed onto a bit of lining paper, two coats, and stand it against the wall at different times of day. On a near-black this dark, lighting makes a bigger difference than the ΔE figures suggest, and one will simply *sit right* in your space. Most people land on Raven Plume — but trust your own eye in the actual room.