So.....We have recently been joined by an au pair for half a year and as a fully paid up member of the computer youth movement

she is busy Skype-ing family, friends and boyfriend for several hours each evening. The rest of the time streaming various sites and simple surfing. The wifi is blinking at such a rate that the diodes almost look like they're not blinking and this has got me thinking.....We have a (generous) bandwidth limit per month, but at the rate the au pair is using her laptop i am afeared that the limits will be breached long before the month is out.
I've tried Google, but most of the results are from several years ago and there didn't seem to be any real numbers of the usage that Skype can generate. Has anybody got hard numbers or even anecdotal evidence through experience ? I am aware that if your connection is set up as supernode or not will have an effect as well. Anyhow, any and all answers/advice gratefully received.
SHJ