ios9.0.2 has broken my wifi on iphone 6

I downloaded ios9 with no problem then a couple of weeks later downloaded ios9.0.2. On restarting my iphone I cannot switch on the wifi and the button remains greyed out.

I have restarted the phone and connected to iTunes but cannot solve the problem. I took the phone to my local o2 shop who tried to fix and could not so they sent it to there apple repairer.

They will not repair under warranty because some time ago I had a screen repair carried out by a non approved apple store. They have quoted me £480 to repair.

Naturally I am not accepting the quote as the phone is only 6 months old and apple caused the fault to the phone with the download. If the phone worked before the download they should uninstall the download and take it back to its state pre download. If they cannot do this they should repair under warranty.

Apple cannot say it is my fault as you have to have wifi to install the download.

If I sent my VW back to a VW garage to have the diesel software problem fixed would my warranty be useless if they blew up the car but found I had previously

replaced the windscreen wipers at a non VW garage ?