So there were a lot of adverts going around for Sky showing off the new undelete function that they had, whereby if you (or someone else) deleted a program accidentally (which is easily done as I have found to my cost when backing up from something you are watching, hitting delete straight away, and it deleting something completely different because it had just recoded something else while you were watching your program!) you could recover it.
However, what the adverts did not show, was how do you actually undelete something on your Sky box? In theory it is quite simple but in practice it is much easier to find if you know where you are going (much like anything really!). So, to undelete a program, go to your Planner and you will be taken to the All programs section (the place where all your recorded programs are). Without pressing the down arrow to go to the programs, skip left and you will see the Deleted section. From here you can see the programs that you last deleted. Programs will be kept here until you need space for further recordings so if you do have plenty of space on your box it should be no hassle to go back and retrieve a deleted program.