The "spare" lines above and below the picture are pretty limited as to how much information they can carry, and haven't changed since Teletext was invented to make use of them. You'd think some boffin might have devised an algorithm to use them more efficiently though...
I prefer the old analogue Teletext service to the new digital text service.. Am i the only one to notice that the pages load up a lot faster. I will miss it when they eventually turn the signal off :(