I've not seen the Sky HD commercials but I have just been to the Sky HD site, where, in my view, it's pretty obvious to visitors that they need an HD ready TV set.
It says this (in the HTML site):
Make sure you get the most out of Sky HD with an HD Ready television
Because a High Definition picture has over four times as much picture detail as a Standard Definition picture, you'll need a TV that can display all this extra picture detail. These TVs are called HD TVs.
If you haven't bought an HD TV yet: Look for the HD Ready logo. This labelling scheme is being supported by all major TV manufacturers to help you find the right HD TV. Sky HD is designed to work with HD Ready TVs. Sony offer a range of HD Ready TVs.
If you're not sure if your current TV is HD Ready: Check your TV's manual or contact your retailer. Sky HD is designed to work with TVs carrying the HD Ready label. The Digital TV Group website contains a list of TVs that are HD Compatible. If you are still unsure there is more information in our FAQs.
Bob