Well, of course David Tennant is Scottish. 
Not quite right. K9 model I left with Leela, back in The Invasion of Time. The fourth Doctor promptly built a new model. K9 model II left with Romana in Warrior’s Gate. In the spin-off one-shot K9 and Company, it was revealed that the Doctor had built yet a third K9 and sent him to Sarah Jane. It’s this K9 mark III that appears in School Reunion.
Dear Lord, does this mean he will be even less comprehensible to an American-speaking audience (or even an English-speaking audience) than Eccleston?
I swear, there are times with Eccleston that I’ve felt I should turn on my TV’s captioning.
Fear not; he doesn’t use his actual accent most of the time - it was just ( I think ) for an episode where they were* in * Scotland.
Lots of planet have a north.
I understood them all just fine. But I sometimes wondered if anyone over here had a problem with Rose losing consonants.