It sounds like you're confusing what ITV1 HD is showing.
If you watch ITV1 on channel 3, then you'll get your local news and ITV National news.
However, as there is only 1 HD feed for the whole country at the moment (satellite and freeview HD), there are no regions, therefore ITV show London Today/Tonight as the "local" news programme on ITV1 HD and then the ITV National news as normal.
Both London Today/Tonight and the ITV national news are produced in standard definition, and upscaled to HD resolutions by ITV.