W^D Models have a fantastic looking WW1 Thornycroft available. The kit looks to be very well detailed, and includes decals. It seems to be available from their own websitehttp://www.wdmodels.com/
Tom Cole built and painted this one:
Here's the unpainted version:
And there's some discussion with more pictures here:
Definitely on my shopping list! WW1 softskins are hard to come by.