The cellular data services have disappeared from my settings. Can anyone help me restore it please?

Try this - Reset the iPad by holding down on the Sleep and Home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider - let go of the buttons. (This is equivalent to rebooting your computer.) No data/files will be erased. http://support.apple.com/kb/ht1430

 Cheers, Tom 😉

Are you saying when you go to Settings, the green Cellular line doesn't show or it's gray? Or when you click on Cellular the Cellular Data line doesn't show or is gray? Have you slid the button to the right to turn On?

Is your iPad jailbroken?

 Cheers, Tom 😉

Try - Restoring iOS software

http://support.apple.com/kb/ht1414

 Cheers, Tom 😉