I've decided that frames are definitely not the way ahead, so I've opted to keep it simple this time around. To navigate around the site, just use the image maps and links. There are three icons (shown below) in the top right corner of every page except this one, which should take care of the rest:
The blue arrow is just a 'back' button for people browsing in full screen mode. The middle one returns you to the start of the section you're currently in, and the little house at the end will bring you back here. Simple, eh?