I understand it can be frustrating that you can't share all your builds here on the Airfix Forum, but we decided early on that the Airfix website shouldn't actively promote other manufacturers. Now, we aren't ignoring or turning a blind eye to the fact that other manufacturers are involved in this hobby of ours - we know that aftermarket parts are used, paints, decals etc. but the important point here is that these still involve Airfix. As with our Customer Image section, the website requires simply that Airfix be involved in the build or what's being shown.
It's great that there's other manufacturers in this hobby (without them, our suggestions list would be five times as long!), but I think it's reasonable that we've made the decision not to promote them on our web space. This means that any builds, images etc. that focus solely on something that doesn't involve Airfix aren't permitted. I feel that's a reasonable balance and one that falls in line with the website as a whole.
If you still disagree with this policy, please get in touch with me privately (using firstname.lastname@example.org). I don't think much good can come from continuing the debate here and further pulling this great thread off topic.