Some people might not be aware that there are two Sky+ Planner sorting options ....
1) With All selected on top - Press Green A-Z
All programs are sorted in strict alphabetic order regardless of when they were recorded.
If you press the down button and type a letter,
The recordings for that letter are in strict alphabetic order.
2) With All selected on top, just press the down button and type a letter.
The recordings for that letter are in chronological order.
(with the most recent recording at the top)