Thanks for the support guys. These boards haven't been tested for moisture content yet, but that's a priority so I know what I'm working with. I accidentally left them standing against my cab and rushed off to work before popping them into the workshop. The sun hit the leading boards and, hey hey, cup goes the weasel.
Since these boards are about 10-12mm thick (7/16" > 1/2") I think I'll need to re-read the advice in this thread (just done a once-over relevance check as customary!) and get a plan of action into my head.
I actually want to thin one of the sets out by either re-thicknessing the non-bookmatched side or getting somebody to resaw and open out a new bookmatch on each piece. Given that in a perfect world I'd end up with two 4mm thick boards, how flat would they need to be to get them resawn nicely, and how many problems can I expect with the wood stabilising immediate after cut (I know this has been mentioned previously in the thread, will re-read) and during the re-equalisation process? If resawing 1/2" boards is impossible or has potential for the boards becoming write-offs, I'll ignore this path and get them thickness sanded. Either that or hold my horses and get them flat and stable first. Anyway. Motives clear mind open etc.
The other set will be going onto a carved top instrument of some description. No point in planning this too much lest the buildbug bite. Wood must settle Daniel-san.