Thanks, WD, useful information. The comment about potatoes being high GI sent me scurrying to the internet, where I discovered far too much information. I will be trying the potatoes out soon, and maybe take IDP's idea of adding butter/oil. I can't take the sweetness of gels, and I find potatoes to be a good pre-race meal (better that pasta for me), hence the interest.
Since this thread is actually about Jelly Babies, I should mention them as well. There, done it.