[lasitha fernando]

A few minutes later, the update finished and it booted onto a different wallpaper to usual. The buttons on the side still work fine; volume, wake up, etc, however the entire touchscreen is dead. It doesn't vibrate when I touch the windows/back/search buttons and it does not respond at all- not even the slightest, to presses or gestures. Is this a hardware problem that coincidentally occured the same time as the update; or has the update broken my phone? Any suggestions to repair this would be greatly appreciated! Thanks

[FinDev]

First you should try to simply reboot your phone.
If it didn't work you should try to restore your phone using Windows Phone Recovery Tool.
Link: go.microsoft.com/fwlink/p/?LinkId=522381

If that doesn't work there may be some problem with the phone itself.