GreenFree 2 for 1 vouchers

[maccboy]

My kids have bought me 10 of the above vouchers. So far, I've rung 6 courses that are listed on GreenFree's site and none of them accept the vouchers. Some say they've told GF, but are still on the list, and some say they've never accepted the vouchers.
GF say their list is up to date and that they take off clubs that say they don't want to accept vouchers any more - none of which helps me!
Has anyone else used GF vouchers, and what are your experiences of them?