[AndyCambs]

Not many airports now require you to switch on electronic items - some however do require you to take the laptop out from the case when it goes through the x-ray.

Depending on the airline, you may be entitled to one carry on luggage plus a laptop case (most scheduled airlines e.g. British Airways have relaxed the restriction on one piece of hand luggage). If hand luggage is weighed, then I tend to stuff the cable and power unit in my pocket to save weight.
I have a laptop rucksack which I carry mine in - means you can use it at the airport. UK airports have wifi zones but they're chargeable. Overseas airports (US and Canada I know of) tend to have free wifi which whiles away the time waiting for the plane to board - plus you can check your flight is is actually on time!
Never put the laptop or anything of value in your checked baggage