Could be the screen finally failed. It happens with updates.
Before arranging for a repair or visit to a genius bar, first try a Forced restart
Click here > Force restart iPhone – Apple Support (UK)
If no better you should probably arrange a repair
Click here > iPhone Repair & Service - Apple Support
Or
Click here > Contact - Official Apple Support
Anything other than Screen or Battery may be a replacement phone and the price is in the article under "Other damage"
See also: Get your iPhone, iPad, or iPod touch ready for service - Apple Support
There is no compensation for hardware that fails during an update.
Regarding the Series 3 , once the iPhone is up and running there is not a lot of memory on board and you may need to erase it before trying to Pair.
Settings, General, Reset, Erase all content and sertigs