So, finding ourselves in a serviced apartment with only one network connection (in the bedroom!), I took it on myself to find some WiFi tethering options for my PC (given that I can do it on my phone, surely it wouldn’t be too difficult?).
Well, actually it wasn’t in the end. I needed to update my Intel WiFi chipset drivers and then install My WiFi. The critical part was to put Avast into Internet Connection Sharing mode: without this it blocked any tethering.
Neat, and now we can Skype in the front room using the MacBook Air, so long as the other laptop is on…