Wow! Many thanks for all the hugely helpful replies, everyone, I really didn't expect such a great response.
(By the way, ctg, I'm female, Ali's short for Alison
And I have finished a 105K fantasy novel -- it's only in the last year that I've started trying short fiction.)
I think from all the advice above, I've realised:
- My fantasy ideas tend to be novel-length
- My sci-fi ideas tend to be short-story length
So I'm going to have a go at a few more sci-fi short stories, and see if I can piece together something that I'm happy enough with to submit to markets. And I agree with all those who've said it can at least hone my writing style, and that every little helps on the writing CV...
Cheers again for all the help, you guys rock
Best,
Ali