I had several problems with iPlayer Global on iPad and streaming content to AppleTV, namely, it just didn’t work. It turns out I can blame Apple.
You need both iOS 5 on the iPad and the 4.4.2 firmware on AppleTV. The only problem is that you can’t update to 4.4.2 using the AppleTV update mechanism on the device, because Apple pulled the update after it bricked numerous devices.
However, if you are determined to get this to work, you’ll need to connect the AppleTV device to your computer directly using USB. You might need to buy a USB mini Cable, Type A standard to Type B MICRO for Mobile Devices, 1.8 Metre (6ft) if you haven’t got one already (no Apple don’t include one with AppleTV). Disconnect the power and everything else from your AppleTV with the exception of the USB cable. Open iTunes and you should see the AppleTV device. Go through the upgrade option.
You device should now be running 4.4.2 instead of 4.4.1. AirPlay should now work.