The BBC iPlayer radio app is going to stop working in January on iOS7. I understand the overhead in supporting multiple platforms, so I'm not going to complain about that. The iPlayer will still be available on the web though.
I general listen to iPlayer radio while I'm washing up, which is around 6:30-7:30. I generally miss the start of the Radio 4 6:30 comedy slot, so I often listen to the previous working day's programme instead. In order to speed navigation to the previous day (or the one before that) I've made this page which will take you to the evening schedule for 1, 2, 3, or 7 days in the past. Enjoy.
iPlayer Radio 4 on previous days