Thanks for the responses. (I thought I responded months ago, but I guess I never hit Add Comment.)
Anyway, my hardware is now firmed up, it is a Pi Zero (it's provided as-is onto an interface board), but I will not be running Linux unless I can help it, it adds too much complexity for me and an unwanted boot-up time - it's a hobby system.
If I can find a Forth for it, great, if not, I'll probably stick with what's provided i.e. C.