In reply to dh73:
I'd just run without a club, you can volunteer without being in clubs but races need runners, by running you are supporting races.
I volunteer at a few races, I'm taking down course markings at a 50k soon that I'll race and then walk around after and help take down the course.
When I have my daughter at the weekends and can't run when my wifes working I'll marshal with her.
But it is certainly acceptable to just race.