You'd assume wrongly!
DO: yes, I'd prefer formal English for the national broadcaster's pronouncements, too. There are millions of people who watch the BBC whose first language isn't English, and lots of abbreviations are quite difficult for many of them to comprehend. I think the Beeb has a duty beyond the mere conveyance of information, and that's to present the simplest and clearest possible standards in both spoken and written presentations. They are, after all, our televisual flag-bearer, and should take pride in their efforts, rather than make any ill-conceived attempts to be 'on trend' by cutting corners. As for the ITV stuff - talk about dumbing down! Often very flimsy notions of what counts as 'news', and there's a lot of sentimentalising by presenters about certain stories, which is not what I consider professional presentation.