Front windscreen washer not working

My front windscreen washer is not working. By reversing the connections on the washer bottle I can wash the front screen with the rear button.I took it to the dealer who did not believe me so changed the pump then tried the diagnostic machine,finally said it was the switch. Now they wonted £40 to trace the fault that I had Identified and £300 for the switch. They have now broken the pump motor. I paid and left.
I now wish to fix the problem myself though retired I have spent over 40 years as a car development engineer.
How do I deactivate the steering wheel airbag so I can remove the steering wheel to change the washer switch.