Excuse me for going off-topic a bit, but why would I want to root my device when everything is backed-up onto Play?  The only reason I've seen that i'd want to root is to use an external USB drive but I use Nexus Media Importer & File Manager for this which seems to work fine.

This is a stock Nexus.  I have a number of Apps that use WiFi including The Mail newspaper, Tripadvisor, Linked-in, iPlayer, Youtube, Weather Channel, Sky, Skype, BT WiFi.  I cannot determine any pattern as it occurs when I use  & also when my daughter uses it (her Apps are somewhat different to mine!).  It happens at different locations & it seems like the WiFi just stops working - it loses all coverage on all live wifi signals (both unsecured & secured eg. neighbours).  The previous Nexus I had used the same apps & locations with no problem.
I'm guessing I'd be best off getting another replacement...?