Have just tested it on another WiFi and no luck there either. I am now sure it is a hardware problem as I have done a hard reset and tried everything at the router end. Also my experiences seem similar to those of @peter_goldi here Can't connect to wifi and others here Unstable Wifi connection - and that turned out to be hardware related. Perhaps the wireless antenna daughterboard has come loose. Annoying as it has only just been repaired …
Thanks for the advice everyone.