Hi Callum, I'm quite looking forward to seeing you get stuck into this project. Watching your video you mention mk V tanks, a war games company manufactures a whole range of WW1 20mm stuff including mk.V tanks. They are available here if you're interested http://earlywarminiatures.com/product-category/ww1-1914-1918/
May i ask where you purchased the Minitrains set from?
Kind regards
Jaymes