I would contact them directly and nicely ask for an explanation, see how they respond.
Stating you have dated versions of your work, marked in an official setting as proof and that you had been floating these concepts pre the commencement of this campaign and that although ideas are mimicked all the time, this is a straight rip-off and unacceptable.
They may respond well, you may get vindication, but demand a response then release the hounds if they don't reply or your not happy with the response. Mention your a keen blogger and established member of the design community.
Brinke van Zyl, Tim Church have some explaining to do.
Hey I've been down the track of following up on copyright and it is basically just an expensive waste of time. You need a lot of money to be able to do anything about it in Australia i.e. take it to court which costs $20k plus last time I enquired and following up in another country would be even harder. If the warning letters from your solicitor are ignored there's not a lot can be done so in my experience the copyright law does not really do much to protect single designers. Perhaps this company is a member of a professional organisation who would like to hear about it? I guess that's another option.
Perhaps you could use this to your advantage in some way. Seems like an interesting opportunity for promotion of your own talent... you'd need to have a sense of humour about it in that case perhaps as no one likes to hear these stories really :)
But best advice I have: find a way to move on... as hard as it is. The time you spend following up and getting worked up and annoyed is not worth it let alone any cost if you decide to take it further.
@gammagirl - i completely understand and know i have to drop it. looked into it, not much i can really do.
they made it first, it is a completely shit thing, but I've gotta let it go, and maybe put a twist on it, place the ads in my book and have a laugh at them plagiarising it.