Nick, after I read your question, I thought I'd go and have a look at the control panel. Although there seems to be a skin configuration for large fonts and also an edit skin setting for font size, neither seemed to make any difference for me. Anyway, having played around for a bit, firstly I can't help with your question and secondly, try as I might, I can't get back to the default setting. So now I also need help. :)
*kick can*, I've been working on that section the last week trying to get a similar issue with fonts resolved. I thought I could do it nice and quietly, but evidently not. hehe. Give it a week to settle down and then try it.