Argh! Can't connect to home wifi!

Argh!

MBP Retina with OS 10.10.2

I have been having some connection probs, so followed advice here on moving files in /Library/Preferences/SystemConfiguration. This left me unable to connect to home network. Strangely I can connect to BT Fon on the same router - which works fine, but means I have to log on to BT each time I use it.

I have tried changing channels, and forgetting the network etc. and no joy. Other devices are working fine.

Any ideas very welcome.