Hi @JohnNairn, I am sorry to hear about this.
If i understood you correctly you are unable to swipe down on the display to access the quick settings in the phone, am I right?
Firstly I would suggest that you check whether the touch screen is responsive or not at the very top of the display. This can be done using the test function in the Support app. Find and tap Settings > Tap Support > Tap Xperia Tests > Touch Screen
Another thing you can try is to reboot your phone in safe mode and see if you can access the quick settings there. All apps downloaded from Play Store is temporarily disabled in Safe mode and by doing this you can see if it is a downloaded app that is causing this. For more information on safe mode and how to use it click here.
If none of these measures manages to improve the access of the quick settings I suggest that you try to repair the software in your phone using a computer and Xperia Companion. Please note though that a software repair will erase all user data from you phone, so make sure to do a backup before proceeding with the repair.
Try these measures and let me know how it goes! 
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