Are you wearing the wetsuit on the run?
Bodygilde under the arms will help. You'll be glad of the arms if there's a coasteering section again.
I often thought of wetsuit to the hips for keeping legs warm in the kayak but you need to tuck the arms inside or tie them off so they are not in the way in event of capsise.
It's a shortie wetsuit http://www.mandmdirect.ie/01/details/FQ635/Board-A...
that I got for €23 cause Mike said we'd need it for the sea kayak. I've only worn it for an hour on my 'kayak erg' and while it was comfortable enough at the time, I got chaffed under both arms. Can't be having that! I did wonder if chopping off the arms would make it less warm though