The figures are from W^D Models delightfully characterful range. The Mk1 is the classic Airfix kit, while the MkIV and Whippet are Emhar kits, the 18" howitzer (front left of the layout) and tractor are Roden, and the refuelling truck is Skala. The big gun dead centre is a 9.2" howitzer, and it's an A Wilkinson 3D print. Can't find out on his series of videos what the B-type 'bus is - I'm guessing it's either W^D or the Airfix kit, (Edit: and I'm wrong, it's a Corgi from the WW1 Centernary Collection.)
Really rather fabulous, I think. Lovely attention to detail, and clearly lots of thought gone into the staging of each vignette.
Would you like to see something like this on display at a wargames show?