If you want Pavilion Gray on a Dulux budget, Slow Living is your best bet. It comes in at ΔE 2.1 from the original, which is well inside the "very close" band — most people couldn't pick the two apart on a wall. Its LRV of 52.6 keeps it in that same light, airy register Pavilion Gray is loved for.
Running a close second is Silver Shores at ΔE 2.4 (LRV 50.5). Still a genuinely good match, just a fraction further off and a touch darker. If you've got both to hand, go Slow Living — but Silver Shores won't let you down if it's easier to get hold of.
Now, the honest bit. Pavilion Gray is one of those F&B colours that does clever things with light — it leans cool and almost duck-egg blue-green in north light, then settles into a soft warm grey in the sun. That chameleon quality comes partly from the depth and complexity of F&B's pigment load, and no Dulux match will read identically across every light condition. The ΔE figure measures the colour under standard lighting; it can't fully capture how a paint shifts through the day.
So my advice: don't trust the match figure alone. Get a Dulux sample pot of Slow Living, paint two coats on a bit of lining paper (an A3 sheet at least), and prop it against the wall you're actually doing. Look at it morning, midday and under your evening lights. North-facing rooms in particular will tell you fast whether the cooler cast suits you.
If after all that the colour just isn't quite singing the way Pavilion Gray does in the showroom, that's the £20-a-tin premium talking — and only you can decide if it's worth it. For most jobs, Slow Living gets you there and sorted.