Many thanks @Flying Snail @Ironroad and @Mol_PMB for your helpful replies. I am keen on sticking to the steam era but those Bulleid wagons would fit in nicely if I wanted to extend the era later into the 50s. For earlier wagons I'd definitely like to have a go at some kits if available, but I'd also be happy to repaint some British style wagons so it's good to know I have that option as well.
I'm not sure if I'd trust myself at any locomotive kits for the time being, but I might manage to repaint an Irish-looking British loco, would anyone have a recommendation for that?