Restoring from backup when old phone is unresponsive

My old trusted SE has packed in on me. The lightening connector was temperamental (and needed to be supported by several elasticitet bands in the end, before becoming completely non-responsive. 

I have bought a new XR but cannot restore from backup in iTunes because Find my iPhone is still active on the dead SE. I have deleted the old device from iCloud and Find my iPhone app but to no avail. Has anyone encountered a similar issue?