Proven is perfectly acceptable (as in the Scottish verdict of 'Not Proven'), but it's only become prevalent in the last few years in England, I think. Rightly or wrongly, I associate this with the dominance of Scots in the political class, and the way people - not just politicians - tend to ape the language of power.

"Dove" is definitely not standard British English, though possibly it exists in some British dialects. "Dive" a regular verb here. As is "fit": I'm always caught out by "fit" used as an imperfect, too.

As for stepping up to the plate...