I’ve been on an extended fantasy binge for a while now so it’s nice to stumble across a quality WH40k site: Parasitic Studios. The Terragenesis forum also contains a long thread detailing construction of that great Refinery gaming table with photos.
The creator mentions using the ‘Platform’ and ‘Hexagon’ products from The War Store which also look intriguing. In fact, here’s an online review from Terrainosaur.