I've given up & left it to my mate to fix. Hopefully, when I get home it's all good.
There appears to be two seperste issues which ocurred at the same time.
The power cut seems to have led to some sort of corruption of the hdd, causing the wallet & mining program to glitch. Annoying, but repairable. Once I have access.
The second problem appears to be the router. Can't quite figure that out, there were no hard wire connections & the 2nd PC wasn't even switched on at the time. The router clearly still works, as we were using it via tablets & mobiles.
I love a good puzzle, as much as the next geek, just not when I'm trying to work 