OK for some reason if I put the phone into Airplane mode it plays the programs that I have downloaded.
http://iplayerhelp.external.bbc.co.uk/help/announcements/mobile_tab_downloads_3gwifi
Due to a technical issue with some networks and device configurations, playback of a downloaded programme will not work for some users when connected to the internet by 3G or Wi-Fi.
We are aware of the issue and are working on a fix, which will be rolled out in a future BBC iPlayer app update.
In the meantime you can watch downloaded BBC iPlayer programmes by temporarily switching off Wi-Fi and turning off your mobile data connection. To do this on an iOS device go to Settings > General > Mobile Data > Set Mobile Data to OFF. On some devices you might find this under Settings > General > Cellular > Enable 3G > Set Enable 3G to OFF.
Turning off your mobile data connection will allow you to receive incoming calls and texts while enjoying your favourite BBC programmes. However, you will need to switch mobile data back on to receive email or be able to access the internet.