Advanced podcasts 1 to 35 do exist and are quite separate to the Intermediate podcasts. The reason that the first 31 Advanced podcasts are not shown in iTunes is that they were for a charity event - the information about the event is now out of date, and the format changed slightly after these first 31 podcasts. They are still great podcasts though, and you can listen to them in our Advanced Podcast Archives.
The reason why the Advanced worksheets only begin at number 35 is simply because that was the first podcast that worksheets were produced for. The Intermediate podcasts and worksheets are separate - the full Intermediate archive is available here.