I was just cleaning the inside of my car and when I switched the ignition on the airbag fault light has come on have I touched anything that might cause this or is it just a coincidence 

You poked around under the seats? Airbag plugs run through there. 

No just around the dash etc , do you suggest I check under the seats anyway 

Yes, rear seat passengers often kick the troublesome vulnerable connector.

Many thanks I will take a look