unable to sign into iMessage/FaceTime iOS9 iPad

Since upgrading to iOS9 and then 9.0.2, I have been unable to sign in to iMessage or FaceTime on my iPad Air.

It takes ages to let me get into the messages options in settings, then I enter my username and password and it tells me:

Unable to contact the iMessage server. Try again.

Other error messages have been about verification.

This has been going on for three weeks now. I've gone through all the forums and tried the following:

• official Apple advice tells you to go into Messages settings and toggle iMessage on or off - I can't even get into messages to be able to do this.

• I've tried resetting the whole iPad and the network settings

• date and time is correct and set to automatic which another user advises

• I've restarted and backed up I don't know how many times.

• I'm always connected to wifi when I try

Can anyone help? It's really frustrating. I managed to get it working for about half an hour once.