Have you got a 16:9 TV? Because I'm pretty sure at least 85% (if not more) of the country does. Sky News only broadcasts in 16:9 as well, it's not a huge deal.
The thing with breakfast TV is that while many people have a widescreen TV, many also only have a little 4:3 set in the kitchen or whatever, so these types of programme constantly get complaints from people not being able to see the clock properly.
The 14:9 safe area (not shown on that template) is probably as good as you can get these days and still be acceptable by the majority of viewers.
[And yes, it is important, even if it's in a mock, because if your clock has to be in an annoying location that compromises your design, you have to find a way around it for the mock to be any good]